I am no professional but this is all news to me – never once have I heard of any 738 requiring a tech stop on flights from ACE to the UK.
I am a professional and I have had to tech stop en route from ACE to the U.K. in the past. It isn’t common, but it does happen. ACE isn’t the longest of runways, and if you have to take off towards the hills you are take off weight restricted. This means that, with a heavy load on, and perhaps a headwind thus requiring more fuel to be carried you just can’t make it.