I saw a few unharassed transmissions near 7.1 MHz florida but the problem is, you can have screened jammers, i.e. jamming only starts when the transmission is deemed to be 'irresponsible', anti patriotic, etc. It might even go through some kind of judge/tribunal/trial etc (a rapid one), to make some attempt at following internal bureaucracy
Half of their game is gathering intelligence on people because you can only get away with jamming someone for so long.
Cuba has been "hands-off" on hams for a very long time, so it is a pretty profound move to start jamming them now.
HF SSB is hardly a "mass audience" mode, as most people, even if they do have multi band receivers can't resolve SSB, so the likelihood of many people hearing "irresponsible" or "unpatriotic" speech is miniscule.
Obviously, the Cuban authorities cannot shut down amateur transmissions from other countries, so the most likely justification would be to block those.
The point about receiver capabilities still applies, however.
If the Cuban ham licencing regulations are similar to most countries, they don't have to have any tribunal, etc.
If hams are deemed to be breaking regulations in some way, they can be shut down, although with the right of appeal.(The authorities can just delay these, pleading overwork)
Or, as I pointed out, just temporarily close the whole Amateur Service.
Of course, for those who really wish the regime ill &
are plotting against it, this will have zero effect, as they will just operate illegally, & as they are unknown, unlike Amateurs, with impunity.