Agreed !

"dog" --> exact match

+dog --> stemming allowed: i.e "doghouse, doggies, dogs"

That would be nice to have

That's how it works. That's how it has worked for years, except you don't need the + symbol -- that tells us nothing.

["dog"] or anything in quotes means exact match, and that's what we do.

[dog] or anything without an operator means we'll generally try to exact match but also might do stemming or synonym or other matching, if it seems helpful.

Agreed, it could work that way (but doesn't). As a computational linguist who has worked a lot in morphology, I support this :).