The methodology is really flawed.
Why Microsoft office and not Lotus symphony which predated it 6 years? There is plenty of open source typesetting software and editors that goes back to the 70s. Why use OO as the comparator?
You want a GUI? Abiword is 1998. A suite? Koffice is 2000.
Why not compare it with VisiOn or WordStar?
And Word came out in 1983, why not start the clock there? Office was announced in 1988, why not there?
Electric Pencil was 1976, that's where GUI word processing that led to WordStar, WordPerfect and MS Word really started, why not that?
Xerox BravoX was 1972, there was a commercial product called the Xerox 860 with it in 1974, why not that? Here's a commercial from 1977, I think that obviously counts: https://m.youtube.com/watch?v=lQb8hgg2gGs
Nope 1990. It's totally arbitrary
All of these have that same flaw. Before Netscape was Cello in 1993, MacWWW in 1992, both commercial. It was a mix of open source and commercial the whole time.
Photoshop was just a knockoff of Deluxepaint which was a knockoff of the Quantel Paintbox https://en.m.wikipedia.org/wiki/Quantel_Paintbox
Here's a video of the use. https://m.youtube.com/watch?v=BwO4LP0wLbY
Again just an arbitrary year.
Besides, in the long history of software, what's open source? Are we talking the cabinets next to the TX-0 at MIT in the 1960s with paper tapes that you could cut copy and modify? The source code published for free in the zines and journals marked public domain in the 1970s through things like flexi-discs? People broadcasting software over CB radio in the 1980s? Only things released after the modern regime of copyrights was collected and cataloged?
It's just sloppy, arbitrary data and therefore invalid conclusions. This is bad science.