My druid halfling when in rat form has 40 hide and 28 Move Silent, how on earth can the umberhulk spot me without having true seeing?

I guess I am asking, the umberhulk can spot my epic sneak, please fix.

They have true seeing.

Technically its "tremorsense" I think, but yeah, it's mechanically True Seeing.

Umber hulks != umber hulk behemoths != umber hulk guardians.