Even as an engineer, I hope FFS no one notices my vacations. It means everything is running smoothly and I actually get to have a little down time and not think about work
Every job I've worked at, when a co-worker goes on vacation, it's up to the other engineers and laborers to compensate. When the manager goes on vacation there's no extra work leftover
Engineers generally don't take over the manager's responsibilities unless they're technical or reporting responsibilites. Generally it's another manager. Most companies require management involvement in P0 incident response for an example. At most companies I've worked at an engineer generally wouldn't be an acceptable substitute. A peer or the manager's boss usually takes it in their absence. It's not unusual that a significant portion of management responsibilities aren't visible to their individual contributor direct reports.
Engineers having to compensate for your vacation sounds like a bad engineering org. Ideally, any gap in engineering should not be missed. If there are fires while you're out, there's something worse going on that needs to be addressed, whether it's bad management or bad engineers