People selling stuff often only get paid when you buy something. The more money you spend, the more they get paid. That’s the way of the world. And that’s ok.
But understand that this is a conflict of interest (theirs over yours).
They want you to take the highest possible mortgage for two reasons. The first is that they’ll get paid more money when you take out that mortgage.
The second is that it keeps inflating house prices so that future house hunters will need to obtain even bigger mortgages to purchase those ever increasing in value houses. And that will generate even more money for them.
Your mortgage broker is lying to you about how much house you can afford