WinScan2PDF uses the TWAIN interface, which makes it possible to communicate with the scanners, an old proven Standard!
Most scanner manufacturers ad here to the Twain standard or support it. For this reason, the range or support for scanners and multifunction devices is very extensive with WinScan2PDF.
The current (Thursday, April 19, 2018) version of the TWAIN standard is TWAIN 2.4, an image-processing program equipped with a TWAIN interface can receive data from any image input device, but the WinScan2PDF is more focused on scanning and thus provides support.
See also: https://www.twain.org/specification/
But to get a program like WinScan2PDF, is not only enough to communicate with the scanner, many more finishing touches are needed until a stable use is possible, every scanner and operating system have its pitfalls and quirks and always against BUGs.
In WinScan2PDF is the Twain Version 1.8 from 1999!
See: ► ... WinScan2PDF FAQ! and: ► ... WinScan2PDF History