Does not seem to be able to change defaults for PDF if PDFExpert is installed

[mkbg8]

I'm using macOS Mojave.

FWIW, the Get Info pane (i.e. Finder's) has trouble with this as well, i.e. setting default app for a PDF file to "Preview" (for ex) immediately reverts it to PDFExpert. So, me opening this isssue is mostly like "what the heck is happening, is there a new way of specifying an association"? Maybe something happening only on Mojave?

[Lord-Kamina]

(It'd be a weird thing for sure) but maybe Preview isn't properly claiming to the OS to be able to handle PDFs correctly?

Those symptoms usually occur when trying to set an app not meant for a particular kind of file to open something. Although it's definitely odd with preview and PDFs.