I hardly doubt this has anything to do with scarcity. People just need tBTC sometimes to test things, and out of this need, speculation arises. And, empirically, people speculate without taking into account scarcity.
I believe it would help, some people have this illusion that anything that is limited holds some value in it, if you could press a button and make an unlimited supply of seashells, it would likely result in less people at the beach looking for them, I am not just speculating here, I had several discussions with folks who were hammering tesetnet3 with S9s back in the day, they generally don't intent to screw CPU miners, they just think testnet coins are fun to have, and obviously, some of them, would want them so they can re-sell them to devs who can't mine them, so by making the total supply = infinity, it would most likely drive many of these miners away.
Then only ASIC miners will mine. The goal should be to allow CPU miners to test mining blocks.
Can CPU miners mine testnet4 now? they can not, so at least, if this isn't going to be solved, someone with an ASIC can still find blocks, because as it stands right now, you need and ASIC + selfish mining which requires some programming skills + the time to do so, so it's only a tiny set of people who can mine it, if I am developing a wallet or something, I rather rent an ASIC miner for a few dollars than having to spend days playing with the code and running a few nodes to perform selfish mining, so while it's not an optimal solution, it certainly is better than the current situation.
Once per two weeks, there is a difficulty adjustment, and then, only ASICs can mine a single block. Recently, it took one hour. And before that, there was a time, when it took around 4 hours. And ASIC miners could simply block all CPU miners, once per two weeks, if they would just stop mining.
The guys who control testnet4 have been maintaining the difficulty at almost flat for almost a month, they can do so because it's only them finding the majority of the blocks basically at the time they want.
If no CPU solves the block for 20 minutes, then the difficulty drops to the minimum for everyone. Then, even if you have some ASIC, you have no other choice, than to mine at the minimum difficulty
It drops for everyone but that's just on paper, a person with an ASIC miner would still be able to fork the network with his longer chain, even at a difficulty of 1, the average (more so the high-end) CPU would need a few minutes to solve a block, whereby with an ASIC it could be less than a second, again, even if your CPU was lucky enough to solve a block right at that 20 mins mark, once he receives it, he would still be able to mine 6 consecutive blocks and make you lose your block.
