79jasper
Chickenhawk
I had read that it was to do with the tight clearances. Which is why they're a little harder to shift when cold.the friction material used on the inside of the syncro rings is the reason why ATF should be used. (see pics) that being said, I too have used 50wt genuine dino oil as a trans lubricant on a very high mile ZF5. the syncro ring in the pic is what a wiped out syncro ring looks like.
But your explanation makes perfect sense also.