Media Create had Xenoblade Chronicles 2 at 296k at the end of 2021. It should be over 500k with digital thanks to vouchers.

Weird fluctuations in the PS5 software, prior weeks have Horizon/GT7 floating in top 30... Hardware sales double and the software vanishes lol

Whats interesting is that despite having a userbase slightly more than 2x bigger, Switch doesn't appear to be stealing much Playstation users for most cross gen games. One would assume there is pretty strong cross over between the platforms ownership but the sales disparity always look pretty close to 2:1. If owners of both platforms were typically preferring to play on Switch instead of PS, you'd expect to have an even greater ratio towards Switch. 

Why what? Why would someone who owns both consoles buy it on Switch? Well because the portability. So either users are happy to compromise portability
...or the userbases are quite different and there's not as much cross over between Switch/PS owners as I would expect. 

And the legs, Switch crushing ps4 games in long term. Same time launch, some games were a better launch on PS4, and in the long run Switch is bestseller SKU. One example of Switch legs. 

09./06. [NSW] eBaseball Powerful Pro Baseball 2022 (Konami) {2022.04.21} (¥7.500) - 6.021 / 183.229 <80-100%> (+6%)

20./20. [PS4] eBaseball Powerful Pro Baseball 2022 (Konami) {2022.04.21} (¥7.500) - 1.649 / 91.625 <80-100%> (-20%)

First Week

1./00. [NSW] eBaseball Powerful Pro Baseball 2022 (Konami) {2022.04.21} (¥7.500) - 92.724 / NEW <40-60%>

02./00. [PS4] eBaseball Powerful Pro Baseball 2022 (Konami) {2022.04.21} (¥7.500) - 54.539 / NEW <60-80%>

This is still 2:1 though, are there examples of games where the Switch version has sold notably more than 2x PS4 version?

NSW] Attack on Titan 2: Final Battle (Koei Tecmo) {2019.07.04} (¥7.800)
2019 CY {2018.12.31 - 2019.12.29} 097. - 46.932 / 46.932
2020 CY {2019.12.30 - 2021.01.03} 160. - 23.257 / 70.189
2021 CY {2021.01.04 - 2022.01.02} 099. - 39.780 / 109.969

[PS4] Attack on Titan 2: Final Battle (Koei Tecmo) {2019.07.04} (¥7.800)
2019 CY {2018.12.31 - 2019.12.29} 138. - 28.603 / 28.603
2020 CY {2019.12.30 - 2021.01.03} 570. - 2.318 / 30.921
2021 CY {2021.01.04 - 2022.01.02} 591. - 2.224 / 33.145

059./067. [NSW] Puyo Puyo Tetris 2 (Sega) {2020.12.10} (¥4.990) - 88.954 / 157.670 (+29%) (26.500 <51,35%>)
351./368. [PS4] Puyo Puyo Tetris 2 (Sega) {2020.12.10} (¥4.990) - 5.915 / 11.505 (+6%) (2.551 <27,27%>)
469./803. [PS5] Puyo Puyo Tetris 2 (Sega) {2020.12.10} (¥4.990) - 3.625 / 4.785 (+213%) (476 <12,00%>)

138./000. [NSW] Dragon Quest X: All in One Package Ver.1-5 {Dragon Quest X: Rise of the Five Tribes Online Dragon Quest X: The Sleeping Hero and the Guiding Sworn Friend Online Dragon Quest X: Legend of the Ancient Dragon Online Dragon Quest X: 5000 Year Journey to a Faraway Hometown Online Dragon Quest X: The Maiden of Thorns and the God of Destruction Online} (Square Enix) {2020.05.14} (¥4.800) - 24.961 / 58.885 (4.977 <45,78%>)
409./000. [PS4] Dragon Quest X: All in One Package Ver.1-5 {Dragon Quest X: Rise of the Five Tribes Online Dragon Quest X: The Sleeping Hero and the Guiding Sworn Friend Online Dragon Quest X: Legend of the Ancient Dragon Online Dragon Quest X: 5000 Year Journey to a Faraway Hometown Online Dragon Quest X: The Maiden of Thorns and the God of Destruction Online} (Square Enix) {2020.05.14} (¥4.800) - 4.627 / 20.449 (3.637 <38,05%>)

695./097. [NSW] My Hero: One's Justice 2 (Bandai Namco Entertainment) {2020.03.12} (¥7.600) - 1.617 / 44.229 (-96%) (18.684 <48,07%>)
913./235. [PS4] My Hero: One's Justice 2 (Bandai Namco Entertainment) {2020.03.12} (¥7.600) - 949 / 13.906 (-93%) (6.657 <55,39%>)

112./316. [NSW] Dragon Quest Builders 2 [New Price Edition] (Square Enix) {2020.12.04} (¥4.980) - 32.725 / 40.079 (+345%) (1.208 <14,93%>)
510./767. [PS4] Dragon Quest Builders 2 [New Price Edition] (Square Enix) {2020.12.04} (¥4.980) - 2.933 / 4.216 (+128%) (325 <8,09%>)

131./104. [NSW] Olympic Games Tokyo 2020: The Official Video Game (Sega) {2019.07.24} (¥4.990) - 26.621 / 145.770 (-33%) (8.551 <30,30%>)
407./288. [PS4] Olympic Games Tokyo 2020: The Official Video Game (Sega) {2019.07.24} (¥4.990) - 4.654 / 35.080 (-50%) (4.035 <19,44%>)

459./093. [NSW] Yo-kai Watch 4++ (Level 5) {2019.12.05} (¥6.480) - 3.807 / 99.190 (-91%) (10.885 <17,78%>)
[PS4] Yo-kai Watch 4++ (Level 5) {2019.12.05} (¥6.480) - 3.311 / 11.961 (-62%) (4.321 <36,39%>) - no update

Some I'd expect like Yokai 4 (a late PS4 port) or Puyo Tetris/DQX which are graphically simple games, but I wouldn't of expected Attack on Titan. But you were right, it does seem to be the legs which make the different & franchise affiliation. 

Yeah one should expect a greater disparity for the games considering the PS4 is an even deader console than even the 3DS.