I've been wondering about the mechanics of friction shifting 8, 9, 10, 11 speeds recently. Thumb shifters designed for 10-12 speeds are definitely larger to enable more cable pull, but there are many other factors affecting it. The cassette is wider, but the cogs and chain are narrower. 10+ has different cable pull ratio, and 8+ often have wide range cassettes. Difficult to imagine how that all affects total capacity or ease of shifting in my head without going out and trying it.