What if they actually planned this and fine tuned their ASICs so that they would never be able to actually generate enough satoshis to go above the dust limit? They could tell their users: you've generated 1 satoshi this month, just 5459 more to go ... that's only 454 years :). "Honestly, we want to pay you your share, but the Bitcoin network won't allow it because it's below the dust limit ... trust us, you'll get paid in 454 years".

So they can make them mine fast enough to make a difference in terms of hash rate but slow enough to never actually reach the payout limit - so they could constantly owe their users very small (unpayable) amounts.

If the idea is to mine slowly, it can be done on a CPU. Most smartphones also have a GPU on board, so they could mine faster than a CPU. And the chips are already in there, you wouldn't have to buy a new phone/chip for this.

Finally, people seem to misunderstand how mining works ... you can't mine a single satoshi, you either find a block or you don't, so you either get the 25 BTC (currently) reward + transaction fees or you don't. The pool distributes the load and the reward, so there would still be a "funding" transaction from the pool to the user - it's not like their ASIC can generate 1 satoshi on board, it can lend its hashing power to the pool and receive 1 satoshi (actually 5460+ satoshis, see above) for their effort from the pool.