It's possible their spokesperson was not informed about SimStudio being the basis for Delve. Lots of people in sales and marketing do not know little about how open source software works.
Then maybe say „I don’t know, let me get back to you“ instead of „no, we built it ourselves“?
I'm not sure "Person who answered a question didn't actually know the answer" is such a good defense, almost worse than "We didn't understand the license", because the implications of having such people in your company seems way wider then.