There's a distinction to make between game development and game play/discussion.
Many questions in history-of-gaming are about the early development of various games and play practices. I can see a desire to distinguish these from common elements in the conversation of gaming which were nonetheless never codified outside of discussion forums, and rpg-pop-culture seems as good a bin for that as any.
There is some overlap, of course; successive editions of, say, D&D, or even the development of D&D out of Chainmail, relied to some extent on the experiences people had during actual play of the relevant game. history-of-gaming should probably cover those play experiences that shaped later game development as well.
In light of this, the history-of-gaming tag wiki should be amended to
This tag covers questions about the historical development of role-playing games: the history of game companies, trends within the hobby, developments of new kinds of mechanics, and how gaming's place in culture affected these developments.
For questions about popular elements of gameplay or game discussion, consider rpg-pop-culture. For identifying gaming products from history, also consider product-identification. For definitions of gaming terms and jargon, also consider terminology.
The rpg-pop-culture tag wiki should be amended to:
This tag covers questions about the pop culture surrounding RPGs: famous events, real-life legends, well-known lore, or other items. If it's more famous as an element of gameplay or game discussion than it is for any appearance in a published rulebook, it's RPG pop culture.
For questions about the process of game development, including gameplay or game discussion that would go on to inform game development, consider history-of-gaming. For definitions of gaming terms and jargon, also consider terminology. For identifying gaming products from history, also consider product-identification.