I think these assumptions are the trickier/error-barriest ones. The other, more directly comparable stats suggest reddit is more than 100x bigger than HN. The comment and post numbers here
https://redditblog.com/2019/12/04/reddits-2019-year-in-revie...
make it look like something closer to 500x-ish, give or take.
eyeballing (the purest ancient datamining fu technique) this
puts HN somewhere in the 15th-to-20th-ish top subreddit category by post and comment activity.