Based on Top 100 Japan 2021 by GDL

Time for some splits

NSW/PS4

41./00. [NSW] Dragon Quest XI S: Echoes of an Elusive Age - Definitive Edition [New Price Edition] (Square Enix) {2020.12.04} (¥4.980) - 132.247 / 165.686
86./86. [PS4] Dragon Quest XI S: Echoes of an Elusive Age - Definitive Edition # (Square Enix) {2020.12.04} (¥4.980) - 40.003 / 84.714 (-11%)

47./00. [NSW] Super Robot Wars 30 # (Bandai Namco Entertainment) {2021.10.28} (¥8.600) - 96.094 / NEW
59./00. [PS4] Super Robot Wars 30 # (Bandai Namco Entertainment) {2021.10.28} (¥8.600) - 78.531 / NEW

48./00. [NSW] Little Nightmares II (Bandai Namco Entertainment) {2021.02.10} (¥3.600) - 95.018 / NEW
94./00. [PS4] Little Nightmares II (Bandai Namco Entertainment) {2021.02.10} (¥3.600) - 35.414 / NEW

49./00. [NSW] Tsukihime: A Piece of Blue Glass Moon # (Aniplex) {2021.08.26} (¥7.000) - 94.462 / NEW
53./00. [PS4] Tsukihime: A Piece of Blue Glass Moon # (Aniplex) {2021.08.26} (¥7.000) - 85.877 / NEW

51./00. [PS4] Samurai Warriors 5 # (Koei Tecmo) {2021.06.24} (¥7.800) - 91.348 / NEW
56./00. [NSW] Samurai Warriors 5 # (Koei Tecmo) {2021.06.24} (¥7.800) - 82.104 / NEW

57./74. [NSW] Puyo Puyo Tetris 2 (Sega) {2020.12.10} (¥4.990) - 80.397 / 136.803 (+43%)
PS4+PS5 outside top 100

60./52. [NSW] Sakuna: Of Rice and Ruin # (Marvelous) {2020.11.12} (¥4.980) - 77.418 / 162.232 (-9%)
PS4 outside top 100

62./57. [NSW] Minecraft Dungeons: Hero Edition (Microsoft Game Studios) {2020.09.08} (¥3.600) - 73.996 / 150.780 (-4%)
PS4+XB1 outside top 100

63./19. [NSW] eBaseball Powerful Pro Baseball 2020 (Konami) {2020.07.09} (¥6.980) - 67.977 / 337.625 (-75%)
PS4 outside top 100

74./00. [PS4] FIFA 22 (Electronic Arts) {2021.10.01} (¥7.909) - 54.074 / NEW
75./00. [NSW] FIFA 22: Legacy Edition (Electronic Arts) {2021.10.01} (¥3.909) - 51.764 / NEW
PS5 outside top 100

78./00. [NSW] Fortnite: Minty Legends Pack (Epic Games) {2021.11.02} (¥3.000) - 47.799 / NEW
PS4+PS5 outside top 100

90./00. [NSW] Fatal Frame: Maiden of Black Water (Koei Tecmo) {2021.10.28} (¥4.800) - 37.274 / NEW
PS4 outside top 100

95./92. [NSW] FIFA 21: Legacy Edition (Electronic Arts) {2020.10.09} (¥5.091) - 35.414 / 75.550 (-12%)
PS4 outside top 100
___

PS4/PS5

22./00. [PS4] Tales of Arise # (Bandai Namco Entertainment) {2021.09.09} (¥7.980) - 220.122 / NEW
64./00. [PS5] Tales of Arise # (Bandai Namco Entertainment) {2021.09.09} (¥7.980) - 65.292 / NEW

23./00. [PS4] Resident Evil Village # (Capcom) {2021.05.08} (¥7.990) - 206.312 / NEW
61./00. [PS5] Resident Evil Village # (Capcom) {2021.05.08} (¥7.990) - 74.644 / NEW

30./00. [PS4] Lost Judgment (Sega) {2021.09.24} (¥8.290) - 163.607 / NEW
83./00. [PS5] Lost Judgment (Sega) {2021.09.24} (¥8.290) - 42.743 / NEW

32./00. [PS4] Demon Slayer: Kimetsu no Yaiba - The Hinokami Chronicles # (Aniplex) {2021.10.14} (¥7.600) - 150.560 / NEW
PS5 outside top 100

66./00. [PS4] Judgment [2][New Price Edition] (Sega) {2021.04.23} (¥1.800) - 63.650 / NEW
PS5 outside top 100

70./00. [PS4] Call of Duty: Vanguard (Sony Interactive Entertainment) {2021.11.05} (¥7.900) - 55.708 / NEW
PS5 outside top 100

85./00. [PS4] Battlefield 2042 (Electronic Arts) {2021.11.19} (¥7.909) - 40.707 / NEW
PS5 outside top 100

88./00. [PS4] Scarlet Nexus (Bandai Namco Entertainment) {2021.06.24} (¥8.200) - 38.916 / NEW
PS5 outside top 100

99./00. [PS5] Marvel's Spider-Man: Miles Morales # (Sony Interactive Entertainment) {2020.11.12} (¥5.900) - 34.016 / 66.238
PS4 outside top 100

Source: Install Base(Chris1964)

That Legends Arceus was able to pull off these numbers just a few months after the Diamond/Pearl remakes really shows the benefit of its fresh approach to the series. There's no sign of franchise fatigue, as Legends offers such a different experience.

So whenever there's a multiplat game for Switch/PS4, when the PS4 version of a game outsells the Switch version, they're relatively close in sales. However, whenever the Switch version outsells the PS4 version, the Switch version appears to be outselling the PS4 version more convincingly. Not saying it's happening for all games with a Switch and PS4 version, but a good amount of these games have these patterns based on the results here.

Decent hardware numbers for PS5, but either the PS5 moves no software or all software for PS5 is digitally sold. Most releases seem to survive barely a week in the top 25.

When you know the devs didn't plan to release the game on the Switch, that says a lot

Will be interesting to see how Demon Slayer fares on Switch; it'll be arriving very late, (really no good reason it shouldn't have been on Switch day 1) so presumably the hardcore fans will have already bought it on PS4/5, but then again, a lot of Japanese gamers won't have a PS console and wouldn't have bought one just for Demon Slayer, but might be keen to try it on a system they do own.