Well, I think the dictionary comparison is weak given its explicit purpose as an educational tool, and RPGs in the 80s were only 7 years out from the genesis of the hobby as we know it.
Arneson's testimony in a deposition in Arneson v. TSR makes mention of Educational Roleplaying in 1962 (10th grade) and 5th grade (1957?)... and how TTRPG is in fact related but not the same.
Apparently, Gygax was trying to refute Arneson's credit by making RPGs as hobby a non-invention...
Gygax's lawyer definitely tried to draw that line... and Arneson distinctly and clearly explained the differences and changes between the use as a tool for teachers and a game...
Chances are, given the state of the hobby, unless you know your book is going to be available on a shelf at Walmart or Target, anybody picking it up already understands what RPGs are in the broad strokes.
But even then, its probably still wise to spend these pages contextualizing that explanation to the game rather than trying to speak broadly about the hobby before you introduce your game.
There's often a chance of a novice or even non-gamer finding and reading RPG books/PDFs ...
Plus, the Satanic Panic wouldn't have been prevented by the inclusion of these sections anyway because that assumes the people driving those panics could read. In 2024, over half of Americans are barely literate, and half of them are functionally illiterate.
I'm curious where you're getting those numbers; I know that almost every student I've had in grade 6 was literate, and all of them had parents who were literate - most of them in 2+ languages.
The few who weren't were all Self-Contained Classroom Special Education students... kids who will likely never live on their own, and several of whom barely speak... in a given school of 400-500 in 7 grades, the SCCSES are typically 3-12 students, of 6 of those 7 grades. (special ed preschool and kindergarden were centralized in my district, while K-6 was the standard for most elementaries; when I left, the district was migrating to a K-5 model, with 6th at middle-school.)
Now, the level of literacy varied ... from 4th grade level to college level in students of Grade 6...
I'd be surprised if this wasn't worse in the 80s despite a cultural memory otherwise.
1979 is the US historic low
illiteracy rate: 0.6%. Yeah, that means 994 of 1000 were literate in at least one language, most often English or Spanish.
The 2019 report, which shows levels... but only for English. Functionally illiterate in English is below "literacy level 1" and is a mere 8.1%... considerably worse than 1979, but the 1979 data is language inspecific. I suspect a large portion of the 20% with low or no English literacy are literate in another language, often Spanish. In Alaska, the few functionally English illiterate folk I've met were almost always literate in another language... Russian, Ukrainian, Spanish, or Tagalog.
Refs:
Presents information from 1869-70-the date of the first Office of Education report-to the late 1970s on. The creation of the Federal Department of Education in 1867 highlighted the importance of education.
nces.ed.gov