You're talking about the ease of hardforking Steem versus Bitcoin. You are correct that it's much easier to hardfork Steem.

But freezing of transactions has nothing to do with hardforking. The block producers just have to agree not to put the transaction in the blocks they make and the funds are frozen. No hardfork is required.

So the technical ability to do this is simply a function of the number of block producers that need to agree to do it. Because of pooled mining on Bitcoin, there's not a lot of coordination required (there's just a few major mining cartels or at least that was true last time I checked). Now you could argue that someone could fire up a huge mining pool of their own and get their transaction published that way, but that's not a small undertaking.