It's not like there is any other OS, or even a mobile OS, let's call it Android as an example, that has allowed to install PWAs from multiple browsers for years. If that was the case it would be embarrassing for Apple not finding a way to do it.

Firefox on Androdi can already be set as autofill app for the system having the same functionality as Lockwise. On iOS based on the summary it should be available next month. Granted that it requires you to install Firefox but I doubt that there is too many people that uses Lockwise and not Firefox so this is irrelevant for most.

Other than that the only difference is that now there are more steps to get to the password list as you have to go through Firefox settings instead of just opening Lockwise, if you use the list manually it an additional hassle, but if the idea is to use autofill is not a big deal.