In a Y / Y (or star / star) Xformer setup, when given a nuetral on the H side, can it be a common connection on the X side?

I've looked in Satllcup/Ugly's/American handbook this a.m., no clarity

Looks like it's an SDS along with MBJ, GEC, , but why create a nuetral when given one?

Maybe i'm missin' the obvious & need more coffee?

~S~