"mobility of hashpower"
what this means is that if there is multiple ways to spend hashpower, it will go to the most valuable
please go meditate upon this concept for a few minutes at least before you try to write an expert rebuttal?
Discussion
That's a bad argument.
Let's say that you wanted to advertise on the top of powrelay.xyz/explore then you would need to add pow to your ad. It doesn't matter that mining Bitcoin is a better use of pow, you need the pow to post. So you will do the pow, but only if the value you get from the ad is greater than the Bitcoin you could make by mining.
(this is hypothetical, a Bitcoin asic cannot mine nostr pow)