I don't know this logic for the increasing difficulty in solving captcha when they know that the person other side is human (as he is solving captcha correctly).
That's reasonable. Bots can solve the captcha correctly if it's not difficult enough.
I think they are slowly giving the delayed WOF spin in random basis every user. Some user reportedly receiving extra WOF spin to compensate with the delay rewards from last 2 weeks. Just keep tracking your rewards and keep in touch on this thread.
I can confirm this.
Yesterday, I received WOF spins two times and today I received them three times. More WOF spins will likely be credited to our accounts in the next days.