When i'm going for a loan ....?

I'm going for a mortgage on a new house and while working with my mortgage broker he said he needs my e-trade statments. Do they actually look into all my stocks to see which ones i have and how many and everything? If a bank has access to this information who else does? I thought this was private information. Or is this just a technicality where they dont look into it they just need it on record. Im just concerned cause i think its wierd that i have a private account with e trade that a bank has access to, it concerns me. Can anyone clarify this for me