Digital Immigration Status

Hi

My wife received email saying her dependant visa application was successful and she's been granted for 3 years. In the email they mentioned she can prove the immigration status online and there's no mention about BRP card. I called UKVI and they said she wont get BRP unless stated in the email and she can prove her status using online immigration check. Am concerned this will be a problem when she goes to home country and return back. When boarding flight in home country they surely ask for BRP/Visa.. Am not sure if they accept a printout from online portal.
Does anybody have similar experience?

There are concerns.