Yes, that’s basically the idea. I already know that some centralized services are exactly doing that precisely because it seems to be a possibility for now. Of course may vary by jurisdiction. In any case, even with centralized services some people choose to take out BTC since their target investment will be done in BTC. 
And they nice thing about BTC only would be that it could be done completely on-chain and trustless. 

nyan

If so, why wouldn't that also work with just USD?

Remember that tax law is considered "substance over form" meaning that if a transaction has no value other than to avoid tax, it is disregarded.

bitcoin

Tax Hack - BTC vs. BTC borrowing

Is the idea this?

1. Put up 1 BTC as collateral, borrow 1 BTC as loan
2. Spend the borrowed BTC
3. Keep loan open which eventually is cleared "some time in future" (wink wink)?

If so, why wouldn't that also work with just USD? 

Remember that tax law is considered "substance over form" meaning that if a transaction has no value other than to avoid tax, it is disregarded. 