I think whats being said is that in 50/50 calls, everyone is inherently biased towards players they know better, or maybe even 55/45, or 60/40 calls
This is the same way that a welsh fan knowing the welsh team well but only seeing england when they play Wales might miss the good players in the england team, and vice versa. It's a natural bias, not intentional, but a subconscious one.
I think last time out the decision annoying more people was a Dan Biggar in poor form being taken over a really in form Finn Russell, probably the most controversial of the selections (though I personally wanted Watson to go back then too)
It is a natural thing though, maybe be lessened this year due to him not being in such close proximity to the Wales squad since 2019, not sure if it'll make any difference. Either way you're right, should be an even ish split between england wales and Ireland (maybe slightly fewer irishmen)