I did it once I think, barely remember from very long ago. It is a thing, literally. I assume the software tends to give the ads in a generic order, but some days when there are not enough ads system leaves gaps between the ads, sometimes it takes hours to show another ad but in some cases it is the way it is that you mention. It leaves so small gaps like seconds or so. STILL I sense a great deal of intention of them built up those that way. C’ause it should be so easy for them to fix it into a much more stable one like when the ads run out, you will no longer see any FREE speed up button right after without any delay. Strangely sometimes it warns you as there is no ad available but I observed that those happen only when there are still ads but not much for the day. 'Cause after a few mins or hours it gives ad while the button is still there.
I was awared of this situation for a loooong while, and have been giving extreme care not to get trapped by those click baits. Tbh my approach on this can be easily generalised among the whole game, since JW:TG is like a mine field when it comes to one click destroys everything stuff. TH, market, “one-time” offers, speed ups… They insistently don’t add that feature the system asks “Are you sure?” which should be again so basic, so until then (won’t think it is ever gonna be) we need to be playing the game with full concentration. An exhausting day after, sleepiness, giving care to someone or something else at the same time playing it (feeding a baby, watching tv, being in a conversation and so on, examples are numerous 'cause we are human beings 
) are the biggest dangers that push you into the arms of “bye-bye sources”.
