We aren’t, and we don’t. You are misinformed.

In Britain, the word ‘biscuit’ means a hard baked cookie, like a graham cracker. Since this is the normal use of this word in the UK, we don’t automatically think of the plain scone-type baked goods for which Americans use the word ‘biscuit’. US English is a different dialect of English, and there are many words which have different meanings from U.K. English (jumper, braces, suspenders, tap etc.)

What on earth makes you think we call bread rolls ‘puddings’? In the U.K., pudding is any dessert, not just the blancmange-stuff which Americans use that word for. It is correct in the U.K. to say “I’m having apple pie for pudding.”.