I still don't get this (stubborn) certainty.
This + the information that Sony probably going to get some studios in Japan could impact the so called shift.
This week is a very good week for Playstation. Next week will probably also be a good week for them.
On the other hand they also have weeks where they get 0 titles charting in the top 30. There have been several weeks both last year and this year where Switch has had all 30 titles in Famitsu top 30. Usually, about 1/2 of those titles are Switch third party games. A more average week has 26-29 Switch titles in the top 30, and again usually about 1/2 are third party titles.
We are already there. Switch third party sales already dominate Playstation third party sales in Japan by a huge margin. Considering how obvious it is that the money is on the Switch, most Japanese third party games will end up on the Switch. It's already happening, and it's going to keep trending that way even more.