Hindsight is 20/20, but perhaps you could've only sold 5 given your plan to buy back upon the dip that didn't happen...your timing turned out to be unfortunate, since ASTS starting running away around June 6th.
Otherwise, you might've sold 15 at a far higher strike, say 50, if that was available at the time. While your premium would've been much less, you would've received $75k upon assignment. That would've eased the sting. But maybe you specifically wanted the big premium to buy those UNH calls.
Alternatively, you could've sold the longest term leap then available, probably Jan '27 at that point, at a high strike price, with the extra time boosting the premium back up some amount. Again, ultimately you'd have been paid more upon any assignment.
EDIT: since some of these were rolls, then I mean you could've rolled into what I referred to above.
The data they used was readily available online so I decided to attempt a replication of this to prove them wrong, but it seems like there may be some substance to this. I have used OSRS bonds rather than RS3 bonds since there is a kaggle csv available for download.
I have used the multi-day log returns using look-behind windows, and computed ACF with equal sample counts per lag.
This is with checking through 40 day lag:
https://i.imgur.com/yDtATBh.png
And this is checking just through 10 days:
https://i.imgur.com/i2PI3SO.png
And again through 10 days but using a 2 day log return window:
https://i.imgur.com/m04HZYB.png
I would encourage someone else to also attempt replicating this analysis to ensure no errors have been made.
Edit: btw I am using an exogenous ACF methodology