> ...but I’m pretty sure Citadel is not even a major player [in the options market].
A quick sanity check suggests Vanguard[1], Fidelity[2], Schwab[3], and TD Ameritrade[4] disagree with your assertion.
[1] https://nms606.karngroup.com/vgrd/606a/2023Q1/588e3c62ff
[2] https://clearingcustody.fidelity.com/trade-execution-quality...