no, that's wrong. 50% is a magic number. with less than that, a malicious miner and only undo a few blocks at a time when they run lucky, but the rest of the network will overtake them if they don't publish their side-mined chain asap. but with 50%+1 they can mine in secret knowing they will be guaranteed to have the longest chain if they mine long enough. so with 49% of the network, they can undo maybe 5 or 10 blocks at a time, and they have to publish them right away or risk the network overtaking them. with 51% then can undo 10000 blocks whenever they want without worry. it is a BIG difference and it most certainly IS a magic number.