Yes - there is a moment of weakness when you cross your feet - but one of the main reasons to cross your feet is to turn a tighter circle that someone who's feet are uncrossed.
When I trained judo we would often quickly move through a "cross-footed" stance to get the throw. It wasn't a "stance" per se in that we spent time sitting in it - but to get off certain throws you ended up crossing your feet for an instant. Kata takes little instants and pulls them apart and makes them big and exploded like a mechanical drawing.
I do not do, nor do I teach a bushiken strike at the end
I don't do one either and don't teach one. However this is the name of the technique. (And it is something demonstrated in the Okikukai Sanseiryu Bunkai)
"Hirate mawashi uke neko ashi dachi morote boshiken" is the name of the movement in Seiryu and Sanseiryu - the technique at the end of sanchin after the doubles strikes (the three step off and strike movements) are named "hirate mawashi uke morote boshiken"
So the same thing only with or without the cat stance. Of course I don't ascribe much to these names because they are Japanese names for movements that were learned with Chinese names. So they really don't matter.
But no matter how you do the movement in Seiryu it is my understanding that your hands end in the flat ready ready fight position (hirate kamae).
The sanchin turn doesn't dramatically shift your weight downward nor does it create the tightest circle possible for a human.
I'm not saying these are things that need to be done, I'm just saying that it is curious that Uechi uses a common stance (cat) without the common turn.
BTW Mike - I've enjoyed training lately with your former student Stanley. He's a really super guy.