I think that's about right, yeah - in my experience international gatherings in Europe tends to converge on a sort of continental pidgin English where you shave off all the difficult aspects and end up with this very clear and crisp shared language that's more mutually understandable for everyone involved than any of the ordinary 'native' variants of English.
I think what's less clear is how consistent these convergences are. Certainly I have noticed colloquialisms and alterations to better fit romance and germanic languages that pop up again and again, but at what point does it get consistent enough to be its own 'thing' and not just a handy linguistic tool fashioned for the task at hand?
I would say if German english (Denglish) would pick up French english Idiosyncracies and vice versa, so if the speech patterns aren't just a result of making mistakes in a foreign language, but if they are acquired by other speakers. The Euro-English article gives as an example of Euro-English "Planification" for "Planning" which seems to stem from french / spanish https://fr.wiktionary.org/wiki/planification . So if the Germans start using planification they would have learned it from the french/spanish Euro-english speakers (I never heard "Planifikation" in German although its actually a word in the dictionary, I looked it up). And that would mean that certain Euro-English features propagate throughout Europe and are more than just Denglish/Frenglish/Swenglish and more than just English-learners messing up vocab/grammar.
While we are talking about language, there definitely are also those folks who move abroad and after a few years when they return they have picked up peculiarities of the language of their host country. The daughter of a neighbor moved to Paris for example and after a few years she started to sound more french. Still spoke perfect german but with an accent. Similarly a coworker who is a US expat in Germany told me he caught himself using some Denglish constructions.
I think what's less clear is how consistent these convergences are. Certainly I have noticed colloquialisms and alterations to better fit romance and germanic languages that pop up again and again, but at what point does it get consistent enough to be its own 'thing' and not just a handy linguistic tool fashioned for the task at hand?