First of all, to be false, it would have to be proven that there aren't over 70,000 creatives. Secondly, for all any of us knows 70k is the number of active creatives. Thirdly, activity is relative. I myself have been through periods of inactivity and yet, here I am. Those that are inactive right now, even if they have been inactive for months at a time, does not mean that they won't decided -- for whatever reason -- to come back tomorrow and do a few or even 30 contests. Finally, @Chasity2ku is right, there is nothing on the page or within the advertising that I have seen that implies that you (as a CH) will have all 70k creatives actively submitting for your idea.
In fact, as seen here: on the MAIN page it says that you can expect hundreds of creatives and that's actually about typical. So, I wouldn't necessarily consider anything so far misleading enough to give a false impression on this. Plus, I think, at least there used to be, more information in the FAQs that said this amount as well and also that guaranteed contests would bring more attention which is accurate as well.
In my opinion, the only thing that would give a CH false impressions would be if they decided to plow through everything without reading, and doing their own research. In comparison to the other choices (of platforms and sites which do similar) out there which many of us have also been a part of, SH is still the best in unique ideas, amount of ideas, amount of actual creativity versus people that just do random robotic submissions, and many other things.