Yes, but you can bind to GTK in very easy way.
At least on Linux you can crosscompile with wine for Win aswell. In stark contrast it has a commandline compiler what makes it easy to integrate in your own CI/CD
This is one main reason why I favour PB and even Freebasic. Freebasic a bit more because it is real free (in terms of GNU) software.
True, with all its advantages and disadvantages.
For me Xojo is mainly a MacOS App with Windows and little bit Linux, Mobile and Web. PB is more even in its crossplatform support.