alt Hacker NewsdBase and its numerous descendants and competitors (FoxPro, Clipper etc) were extremely popular for line-of-business desktop applications in the 90s. And, yes, they are indeed traditionally categorized as 4GLs - and, given how nebulous the definition always has been anyway, I think that "traditionally categorized" is the most practical definition that you can use here.
But, yes, I agree that aside from the generally more verbose and sometimes unwieldy syntax, there wasn't really that much to it in practice. I did work with FoxPro, and the reason why it was popular was not because you had to write things like "ACTIVATE WINDOW", but because it had many things baked directly into the language that nicely covered all the common tasks a pre-SQL data-centric app would need - e.g. a loop that could iterate directly over a table.
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Gosh it's a long time since I heard 'Clipper' mentioned. I used to do 'PC' apps for Banks in the early 90s. Turbo Pascal and Clipper were popular with us. (We used PL/1 rather than COBOL for batch processing)
Then VB 4.0 started to get popular around 1996 and ruled the roost...
So many technologies... does anyone remember 'SUPRA' from that era! (think it was supposed to be a 4GL language/interface for mainframe databases)
That class of software also allowed for very efficient data capture against normalised tables. A recall as early as Paradox for DOS (something I haven't thought of for a while) in about 1990 being really simple tools for creating one-to-many database capture 'forms' (with selection boxes, date drop downs, the lot). The richness of form design and tight coupling to the database meant that the language did not need to be very powerful and could just run as a script on top of a rich database environment. The PC-based successor to mainframe 4GL concepts was late-nineties RAD (Rapid Application Development) of Delphi and VB. MS Access was the Windows successor to those tools and was wildly successful as a way for 'business people' to build apps. It took many years for windows low-level app development or the web to catch up to the richness, but they have never really achieved the same level of non-programmer usability.