Noises in the wall, newly purchased, built in 2016

If it is an exterminator, I would trust him first. He will do it properly, maybe the "just quickly drill a hole" part was also just simplified.

I don't know if the pest control technician performs sonographic preliminary investigations – some pest controllers are dull poison sprayers. Thermography is regularly used more by energy consultants. Both with sound propagation measurements and – since a colony of living beings is suspected – with thermal imaging methods, it would be possible before or instead of drilling to clarify what is going on and how large the cavity is. But I have little doubt that there is no reason for naivety.

maybe the "just quickly drilling a hole" was also just simplified.

I really hope so.

Well, take it easy. If it were August, okay, but at this time of year there is neither a wasp nor a hornet colony living there. They all die over the winter. At most, an annoyed queen with 5-10 offspring might come out.

They all die over the winter.

We are talking about a winter in an energy-saving ordinance house, and the OP mentioned some "life" at the morning temperature rise.

I am not aware of any wasps or hornets that overwinter here in Germany as a colony.

die als Volk hier in Deutschland überwindern

With a sealed exit, you can sometimes miss the flight.