I think the Interview with Maximum (Aug, 2022) discusses the lockout and fixed 20-man composition. There may be other interviews/statements, but this is what I could find.
I thought I had read something that fixed 20-man is a single “tuning” point that is less work for the dev-team than a Flex-Size raid composition and also that Ion thinks the pinnacle challenge of WoW content should require an organized guild and not be accessible to PUGs (at least for progression and/or full clear). However, I couldn’t find that assertion (but didn’t look that hard either).
The Google AI summary includes these abstracts:
- Ion Hazzikostas, former Lead Game Designer and current Game Director of World of Warcraft, has discussed the 20-player limit for Mythic raids, primarily as a way to ensure all classes and specs can meaningfully contribute. He’s also emphasized the role of this limit as a “barrier of entry/friction” for Mythic raiding, separating it from the other, more flexible raid difficulties.
- Hazzikostas has stated that the 20-player limit helps facilitate the inclusion of various classes and specs in Mythic raids, allowing each to have a role to play.
- He views the 20-man limit as a way to create a more challenging and rewarding experience for Mythic raiding, separating it from the more casual, flexible modes.
- Hazzikostas acknowledges that maintaining a 20-player roster can be logistically challenging for guilds, but he also suggests that it can reveal fundamental issues within a guild’s structure if they cannot consistently assemble a 20-person team, as mentioned in a thread on Blizzard Forums.
- In essence, Hazzikostas has argued that the 20-man limit for Mythic raids serves multiple purposes, including ensuring a diverse and meaningful role for various classes, creating a challenging and rewarding experience, and potentially revealing weaknesses in a guild’s structure and logistics.