This is false. Quantopian sources their historical and real time data from Nanex, and the data is explicitly free of survivorship bias (i.e. they maintain data for delisted equities).

I don't know what you verified, but it directly contradicts my own experience and the FAQ: https://www.quantopian.com/faq#data-sources

To your second point, as another commenter said Quantopian doesn't see your algorithm unless you give them permission, as outlined in the terms of service (which are very readable, by the way).

NB: I am not unaffiliated with Quantopian and don't use the platform for my own trading, but I have tried it out before.