No. The builders obviously knew what they were doing, especially if their "technical department" confirms it because it's obviously a matter of record.

And there's also the question of what BC don't know won't hurt them, but if you're concerned then get a letter off the builders stating what they have done and why, they certainly don't sound like a firm that would do anything to harm you or, more importantly for them (because they sound like a reputable company), themselves!

They were probably thinking of the traditional "knock through" between a ground floor living room and dining room. That frequently does need approval because the wall is often structural rather than decorative.