But, in furtherance to that: there is no way to reclaim memory which was supposed to be deallocated by any given app aside from rebooting your system.
Wrong.
If an
application is leaking memory then killing that application will free up the memory, given any sane operating system, which all the ones you're likely to come across are, mostly. The operating system knows what memory is assigned to any application and frees up that memory when the application terminates even if the application doesn't do it for itself.
It's only if something in
the operating system itself, rather than an application, is leaking memory that you're likely to need a reboot.