Insofar as graphics went, it's important to keep in mind that prior to the early 1990s, low-level details about how different video cards actually worked weren't necessarily widely known, or implemented in a manner that was hardware-identical to a PS/2 VGA card.
Case in point: VGA (as implemented on the PS/2) actually had support for tiled graphics (in the form of custom fonts), but almost nothing dared to actually USE it (Microsoft's shell for MS/DOS 6 and XM-tracker come to mind as two of the only popular apps that took advantage of it as a way to render a mouse pointer onto a textmode screen... basically, using 9 of the custom characters to render whatever 9 characters happened to be in the 3x3 grid around the mouse pointer, along with the mouse pointer itself). The problem was that there was no official BIOS support for it (at least, not prior to SVGA BIOS extensions becoming a de-facto standard), and there was no guarantee that a given third-party "VGA" card worked in precisely the same way as IBM's official "VGA" graphics... or that the third-party "VGA" card had direct hardware support for custom characters AT ALL. And documentation for stuff like this was insanely hard to come by prior to the first books like the one written by Richard Ferraro in 1990.
It's hard to believe now that you can look up almost anything online, but back in 1989, low-level register details about arbitrary video cards really weren't all that well known... partially, because vendors didn't want to make it easy for competitors to make register-compatible copies of their own cards, and partially because they didn't want to make it easy for the companies whose designs THEY copied to sue THEM for infringement. Unless you lived somewhere like Boston or Silicon Valley, even LARGE bookstores rarely sold books about esoteric programming topics... when such books existed at all.
Going back to the example of Richard Ferraro's book. In 1990, I lived in Miami and went to both Barnes & Noble and Borders all the time. The first time I ever remember seeing a copy of that particular book on the shelves (at the Borders store across the street from Dadeland Mall) was sometime around 1994... and it wasn't cheap.
In retrospect, "most" PC videocards actually DID work almost exactly the same way (at least, insofar as "VGA" was concerned). But at the time, there was an almost-neurotic perception that programming the bare-metal hardware would cause endless compatibility problems... and even if you were willing to live dangerously, the information itself wasn't easy to come by.
In 1992, I was an Amiga refugee who'd finally jumped ship and bought a loaded 486DX33 with S3 '911 graphics card. At the time, I knew that it was possible to program 486 assembly language using flat addressing (or more precisely, using 2-gigabyte segments and setting the segment pointer to 0), but spent MONTHS trying to find out how to actually GET a PC into what we now would refer to as "unreal mode" (in fact, using "the internet").
Even in 1992, you couldn't just waltz into Borders, grab a book about PC assembly language, and expect to find nice chapters coherently explaining things like "Unreal Mode" or "DOS Extenders". From what I recall, there WAS a chapter somewhere in the manual for Borland's TurboASM that touched upon it... but it was purely a minimal reference guide that was utterly incomprehensible to someone who didn't already understand the topic. Information-wise, the late 1980s and early 1990s really were an information dark age. There were lots of books about programming Realmode assembly and making BIOS calls... but absolutely, positively, NOTHING on mainstream bookstore shelves about programming bare-metal hardware. At least, not until the mid-90s (though, as noted, the books themselves started to get published around 1990... you just couldn't stumble over them & had to already know they existed).