[Pyramus]

> When you bake with such flours, you get a denser bread and when you create a starter with them, you'll struggle to get them to double in size for the same reason.

Sharing my personal experience: I use a 100% rye starter (wholemeal or, preferably, German type 1150 [1]) and my starter grows ~2-2.5x in volume. Gluten has an impact but is less important when you proof in a small container (same reason you would bake a high hydration rye bread in a tin). What is a lot more important is that a) the hydration is right, so the starter is not too liquid (in my case a bit less than 100%), and b) you feed the starter in a ratio of 1:3 old:new, or even 1:5.

[1] https://www.hefe-und-mehr.de/en/2014/03/mehl/