If I’m going to hold a lot of cash for a few months, is keeping it in a T bill ETF like BIL a good idea?

Call me dumb but I've been about 75% in cash and SPY shorts since about January. I'm more into trading big macro theses and don't usually spend a lot of time optimizing for fringe returns like chasing .5% in treasuries but I'm holding more cash these days and the nominal rates have improved.

My questions basically boils down to: besides the 15bps of fees, is there any downside to holding my spare brokerage account cash in something like SHY or BIL as opposed to going through treasury direct which is just more hassle than I'm willing to deal with.