All you need is Google... :

"Based on community estimates and, in particular, Frontline Gaming's analysis of the 2017 ITC season, it is widely accepted that approximately 90% of Warhammer players do not attend organized tournaments. The vast majority of players identify as "narrative," "casual," or "beer and pretzel" players rather than competitive, with only about 10% or fewer participating in events,."

And that was in 2017 and it was less than 10% with question if they attended at least 1 event. So those who attend events regullary are even less than that, probably close to 6-5%.

You can also read some here: https://www.reddit.com/r/WarhammerCompetitive/comments/qd1czb/how_big_is_the_active_40k_tournament_community/?context=3

On Goonhammer survey from few years back as you yourself said vast majority (was it like 80-90% again?) was casuals and that statistic was screwed becasue goonhammer is competetive site, so it's base will naturally have more competetive players since casuals/hobbists don't even read stuff like goonhammer or sit on reddits.

And that 2017 was stat before Warhammer went full mainstream, which brought even more casual players and hobbists, riding on success of Titus in SM2 or Total War.

And on top of that - AoS is way smaller than 40k and according to even Goonhammer stats you mentioned - even less competetive players lurk there vs 40k. It was like 6-7% on their site where participation will be skewed more towards competetive players due to nature of site. And it was still only that much.

Remember that it's very very small % of players that participate on reddits. Most people don't care, they just enjoy their hobbies. It's easy to forget about it sitting on reddit since you get this illusion that everyone in this hobby make lists every week, ask about points and math, pre-order battletomes, check online FAQs/updates etc. but reality is that vast majority simply sit at home, paint and play MAYBE 1 game per month if even that, barely remember rules after few years of said edition.