That's new and pretty bad, so I guess the platform failed to stop whoever is abusing their service now reduced the slots and hoping that would put an end. Yeah, maybe this will be the end of the free transaction accelerator. 
I don’t think that was added newly as I have seen it multiple time when ever I try to refresh the page real quick and try to get a free slot, back then I don’t even need to pass the captcha I just need to be refreshing within that little time limit to make sure I see when they will open the free slot but just after 3 refresh and above I always beg that warning which after some times they get it off.