Should still be used sparingly. Not enough Guest Advocates? Pull all but 1 person from SD and put them on a lane. Hop on a lane yourself, or watch SCO while the Advocate there hops on a lane -- and while you're on SCO, hop on the closest lane yourself and do both. Get the ETL-SE on a lane, as well as all the other SETLs. Doing alright on carts? Front of Store Attendant on a lane. Then, if you must, call for backup. SE owns the front. They shouldn't be calling for backup unless they absolutely, positively have no other choice but to do so, which means already having all hands on deck.
.. yet I often see multiple SETLs at the front doing nothing but watching. I see multiple Advocates at the SD despite there being just 1 or 2 guests up there. I see the Advocate at SCO staring at the single guest using it, and nothing else. You talk about expectations of the front, yet you completely ignore all the primary expectations that every other department has. God forbid you have 2 guests waiting on a lane, better call someone away from their push, backstock, pulls, zoning, pricing, and plano workload! That's a joke, and you should know it.
Unless the front is literally on fire, I wouldn't send any of my TMs up to backup. The SD herself can hop on a lane first, if need be.
That's not exclusive to the front end. Imagine being a GMTL and having half your team call off with the other half called to help backup, then having to explain why your pulls, backstock, push, zoning, price change, and plano didn't get done.