I don't think capcha is an example of use beyond "exchange". I think the reason bitcoin can be used in place of capcha is the low transaction costs of the "exchange" (i.e. it wouldn't work with paypal because paypel has high fees, but if paypal had a $0.01 fee then it probably could work in place of capcha as well). Anyway, regardless, a bitcoin exchange in place of capcha it is still an exchange of something of value between the visitor wanting access and website owner wanting to avoid spam.
This critique makes no sense. You are claiming that the non-exchange value doesn't exist because the non-monetary use is useful and valuable and therefore is effectively monetary. WTF? that's the whole point. It's valuable, which is why it can be used as a store of value.
It's an anti-spam and brute force password hacking prevention tool. That gives it value independent of use as a medium of exchange or unit of account, but its utility value makes it a store of value just like a bunch of any commodity is a store of value. Its a commodity.