Well, Nintendo released the Switch years after the PS4 and will release the Switch 2 years after the PS5 so that you will always halve only like half a Switch gen against a full PS gen if you only count the Switch sales till Sony releases a new PS. MS releases everything on PC and soon even as game streaming so that they will never reach 360 sales again (as long as the whole market won't grow a lot) but they obviously know that and care more about their success on all systems combined.
So, yes, if you will count only Switch 2 sales until the PS6 will release, the PS5 will have reach 50% market share. If you will count all Switch 2 sales against the PS5 even some years after the PS6 released then the PS5 probably won't reach 50% market share.
And if you will combine Switch and Switch 2 sales together from the years the PS5 is on the market then the PS5 will probably also not reach 50% market share.
In the end it only reaches the 50% because Nintendo doesn't release their new console just because a new Xbox and PS release.