When I said to make a “Help >> Check for Updates” it was of course on system Workbench for STM32, not STM32CubeMX (I do not even notice there was such a menu entry).
When updating (or installing) the only installable components (plugins) that are tagged Windows or Linux are the external (native) tools like compilers, debuggers...
On Windows, regardless of the running system or IDE version, only 32-bit versions of these are provided as there is usually nothing to earn at running a 64bit-compiled compiler: it will be bigger and will not run significantly faster. However the IDE will run better if running as a 64bit executable as it may manage its memory more efficiently.
Thus when updating a Windows version, you should update the components marked “for Windows 32 bits”. The component that should be updated is the “OpenSTM32 IDE” that should be at version 18.104.22.16850301252 (the last 8 figures are in fact a timestamp).