True. However the need for synchronization is rather infrequent and can easily be done via sneakernet.

There is something else I would like to highlight, about the problem if a single password gets leaked: At least with PasswordMaker Pro I wouldn't only increase the counter for that one site, but rather change it (ideally to a new random number) globally, and change passwords everywhere. The way PasswordMaker Pro uses the counter is that it just gets appended to the input url before hashing. For the hash algorithms that aren't using HMAC this is equivalent to just prepending that counter to the master password, so, a bad actor could just brute-force the combination of increment and master password, and get access to all sites that used the same master password and increment.

So, yeah, that's another big downside. If one password gets leaked, you can either rely on the attacker never finding out that it's a deterministic one, or you can do the same "change every password" dance that you have to perform if your password manager's cloud service data gets leaked.