That has nothing to do with them losing hairs. The hairs are used to discourage predators.
It was something making a guess, not a correct one.
The hairs are on the rear part of the abdomen, and would have little contact, if any, with the substrate as they pull themselves forward under a sperm web. If the hairs came off that easily, all new world tarantulas would be going bald simply manouvering in the tight confines of their burrows. The hairs evolved as a defense against predators; if they easily rub off in day-to-day life, they won't have them when they need them. Same reason venomous snakes give a lot of dry bites; if the run thru their venom too fast, they're at a big disadvantage for a while. Also the same reason real soldiers don't use full auto very often (unlike in Hollywood), as they'd blow thru all their ammo in a few seconds. In all the above scenarios, the primary defensive/offensive weapon is rationed and used wisely. Evolution sees to that.
And how's that again? IF a male tarantula loses any fur at all from crawling under a sperm web, it's neglible. As Stan pointed out, it's counterproductive for them to lose hairs this way. Adult males are out wandering around looking for females, facing more risks and predators than females do, and need to save their hairs for defensive purposes.
It's just that I have 40 years experience with a lot of tarantulas have some idea what I'm talking about. There's a lot of off-the-wall assumptions in this hobby that get perpetuated online. Besides males losing a lot of hairs in sperm webs, some people think calcium causes molting problems, or that Avics need really high humidity, etc. Things get quoted and circulated as fact when they're not. I get 5 to 10+ thanks a day for helping people here.
Stan will be the first to admit he doesn't know everything about tarantulas, or that he's always right. Thanks for staying calm and not resorting to insults. Always appreciated.
I don't think you can tell that after 10 days with a Theraphosa.