This isn't just about non-native speakers but also applies to native French speakers from regions like Quebec or Congo. Despite using similar vocabulary, they sometimes face challenges being understood in France, mainly due to their distinct accents, I mean I believe this also occurs between various region of France
Yes this was covered in my original message. Miss pronouncing a word in French can make it extremely hard to understand for a native speaker. And yes people from Quebec are an excellent example. They will often struggle when their accent is too strong when visiting France. And people are not ill meaning, Quebecois are very popular in France, it's just genuinely hard.
People often don't know that the French language was literally a political weapon to create France. France is political construct, not cultural like most countries. It is an aggregation of different cultures, including different languages. It was vital for France to succeed as a construct to force the idea of "correct French". A French language that would be the same everywhere, without local variations. So yeah, the French ear is not used to dealing with mistakes or strong accents.
No, they did not speak English.
If they had, I wouldn't have subjected them to my French.
Additionally they most likely already knew English and were able to decipher "French broken by an English speaker".
Edit: and since we're sharing anecdotes. I got the same "rude" treatment from Russians when I was learning Russian in Russia, or from Swedish folks when learning Swedish in Stockholm. It's just hard for native speakers to deal with broken linguo, that's just how it is. Swedish people would even reply to me in English, some would call it rude, they were just trying to be helpful and efficient.