Leaving aside this latest 'incident', the subject of whether to select 'standby' is one your (airline) SOPs should address for the aircraft type/s you fly. A couple of the previous threads are
here and
here. As you can see the topic is at best open to confusion.
My view is that care should be taken ANYWAY when selecting codes beginning with 7, and these threads highlight ways to do that. I'm sure that 'passing through' the '7s' will not trigger instantly - nor, I'm sure, would ATC (over)react to a resulting transient 'Emergency' type code squawk although it would, no doubt, focus their attention. I do NOT think selecting S/BY in a busy ATC/TCAS environment is sensible at all (unless ATC or SOP requested) and I would hope no-one does it.