Is there a reason why Let's Go Pikachu & Eevee are being counted as separate games?

Is there any particular reason why these seem to be the very first and only dual release Pokemon games to be counted as completely separate sales entry's on VGChartz?

Would make it difficult and inaccurate to compare and rank the sales of Let's Go Pikachu & Eevee to all the other games because of this:

Pos	Game	Console	Publisher	Total Sales	NA Sales	PAL Sales	Japan Sales	Other Sales	Release Date	Last Update
1		Pokémon Red / Green / Blue Version		Nintendo	31.37m	11.27m	8.89m	10.22m	1.00m	30th Sep 98	N/A
2		Pokémon Gold / Silver Version		Nintendo	23.10m	9.00m	6.18m	7.20m	0.71m	14th Oct 00	N/A
3		Pokémon Diamond / Pearl Version		Nintendo	18.25m	6.38m	4.47m	6.04m	1.36m	28th Apr 07	N/A
4		Pokémon X/Y		Nintendo	16.07m	5.62m	5.06m	4.40m	0.98m	12th Oct 13	06th Jan 18
5		Pokémon Ruby / Sapphire Version		Nintendo	15.85m	6.06m	3.90m	5.38m	0.50m	17th Mar 03	N/A
6		Pokémon Black / White Version		Nintendo	15.18m	5.51m	3.20m	5.66m	0.80m	06th Mar 11	N/A
7		Pokémon Sun/Moon		Nintendo	15.07m	5.93m	4.34m	3.82m	0.98m	18th Nov 16	03rd Aug 18
9		Pokémon Omega Ruby/Pokémon Alpha Sapphire		Nintendo	12.73m	4.77m	3.98m	3.15m	0.82m	21st Nov 14	03rd Aug 18
10		Pokémon Heart Gold / Soul Silver Version Read the review		Nintendo	11.78m	4.34m	2.72m	3.96m	0.76m	14th Mar 10	N/A
11		Pokémon FireRed / LeafGreen Version		Nintendo	10.49m	4.34m	2.65m	3.15m	0.35m	07th Sep 04	N/A
12		Pokémon Black 2 and White 2		Nintendo	8.16m	2.79m	1.79m	3.16m	0.43m	07th Oct 12	25th Feb 18
14		Pokémon: Ultra Sun and Ultra Moon		Nintendo	6.79m	2.27m	1.66m	2.50m	0.37m	17th Nov 17	03rd Aug 18