Leclerc set a lap time 4-5 seconds after Stroll had crashed that put Verstappen 11th. At that point you had the best part of 1 minute 35 seconds on the clock, with a fast lap being in the 1.25's. So there would be very little chance that Verstappen wouldve been able to complete an outlap and make the chequered flag before its fallen, with how slow people go out of the pits on their outlaps. And McLaren could just send out Norris and Piastri in the fastlane straight away and block Verstappen from doing anything.
So in this instance, its not really the directors fault for the red flag making Verstappen miss Q3. Sure, he wouldve been 11th (prior to his penalty) rather than the odd place lower down, but.. yeah.
If you wanna argue the point of red flag being late, then thats another situation. And you gotta allow the stewards SOME time to see the incident, judge how serious it is, before making a decision. I know people would complain if the red flag was waived prematurely. It happend.. last year I think, in Spain with Bottas spinning. And I remember it happend a few times that season, and noone likes that. So you gotta given them sufficent time. What you feel is 'sufficent' is debateable, but in this instance, the red flag didnt really matter for championship.