It’s not illegal to have multiple US passports. US government officials will often have both an official and regular passport, for example. You may have multiple regular passports if you need to travel and get visas frequently. This is all documented, but I wouldn’t be surprised if some border guard grunt doesn’t understand it.

As an aside, I was born abroad to a US citizen father, never applied for a CRBA and just applied directly for a US passport via the local consulate. The paperwork was similar, of course, but the consular staff said that applying directly for the passport was faster and less problematic. I don’t know whether it may be the same in your case.