Prime subcontracting to another Prime

I recently had a situation where a contracting officer suggested rather strongly that we (a Prime on an IDIQ) subcontract to the other Prime on the IDIQ. There are only two primes and it seems to me that suggesting that we subcontract to each other would limit competition. I've seen this in very large IDIQs where there are many Prime contractors, but in this case there are only two. Has anyone else had this issue? The guidance from the CO was verbal. He hasn't given this guidance in writing.