When you swap bitcoin for monero, you have to send the bitcoin to an address on chain. That address is not going to look like a traditional bitcoin address (e.g. starts with bc1), so on chain it can be identified as a swap. Correct me if I’m wrong on that.

But that’s what I mean about leaking privacy. If I own the bitcoin and Feds know I own it, they can reasonably assume that I swapped into monero. So even if I use bitcoin as savings and monero for spending, I still need to practice good privacy in Bitcoin. 

Plus I don’t know any online businesses that accept monero.