I think a well oiled pdship could use it for take out to the optimum level. As far as i know Meckwell plays this rkcb, in fact they play a lot of 4 NT bids rkcb in competition and w/o competition. I know more than just 1 top pairs who plays it rkcb. . I also watch BBO vugraphs, top events, and yet to counter a 4 NT bid as sophisticated and detailed as in BBF. All i see mostly is rkcb unless they have ability to ask rkcb by using other tools such as kick back - minorwood or w/e.
Perhaps we should not only focus on the frequency only. How about the efficiency of a bid ? I mean if you have a bid which is less frequent but what it asks and what it learns is crystal clear information, while we have an alternative use of the same bid which is more frequent (?) but not magically lands you on correct contract, if there is any at 5 level. Basically one of them (kinda )guarantees a result but less frequent, while other one does not but more frequent.
No need to mention the fact that, choosing 4 NT as rkcb you can still show/imply other suits via DBL, but by choosing other one you totally disable yourself from learning keycards. I think using double as take out and totally disabling myself from making direct penalty doubles is better than disabling myself from asking rkcb. Over heavy preempts when we are about to bid at 5 level, slam is in picture most of the time.
Now this is the 3rd time i am mentioning same thing, when you adobt a system where your 4 NT or 5 level bids are sophisticated and complex, you will need time to figure to remember the agreement, time to decide whether you should dbl them and if not which bid is suitable in a timely manner, or all these bids such as 4 NT or 5x or DBL, if made with a hesitation, will open a wide door for complaints from opponents. Because they will not pop up instantly in your memory like a stayman or jacoby transfer. All these positions we have after a heavy preempt or even after a mod preempt are kinda unique positions/auctions. A little detail in the auction may need to be analysed differently in each auction and may require a different approach. You will need time to figure this out and it will almost always come with the hesitation factor. (or maybe my memory sucks and i am getting old

So i am still having hard time to decide which is better tbh. (i meant which is better at the table, obviously 4 NT for other purposes than rkcb is better in forum bridge)