K-xs Close Enough to be Nut Flush?

[Festus22]

I like to play K-xs as a flush draw-only hand (flop 2 of the suit or fold - period!). Is this probability correct:

Assume a 3 suit board. K-xs can only lose to A-xs (forget boats or greater for this discussion). So that hand must have the suit A (18/45 or 40%) and the other card must be the suit (13 - my 2 - board 3 - suit A = 7 so 7/44 = 15.9%). Combining, there's only a 6.4% chance that my K-xs will be beat be an A-xs given a 3 flush board. Of course, when the board shows a 4 flush, now I'm only a 60% favorite. Is this correct? I've had a lot of success with these hands yet I don't see this play mentioned a lot. Unless the miracle K-K-x flops, the key is bailing even if a lone K is flopped.