Privacy issues on pools are almost entirely “what IP is connecting, from where” (as this likely lets you find the physical farm, which is by far the biggest concern with pools). Changing the payout scheme to have more privacy might also seem like it would prevent the pool from knowing the exchange a specific miner uses, but in practice each miner gets a fairly specific amount paid out, so the pool can match payouts with miners. Sure, the miner could go to substantial effort to hide their activities (like taking payout to another ecash mint) but (a) that’s likely to be relatively rare so it’ll stick out anyway and (b) they could do that just as well if the pool just does lightning payouts or even on chain payouts.
I’m not really sure where “simplifies accounting” even comes from, tbh. Accounting for a pool isn’t complicated? You just, like, keep track of a share count for each user. Even with a fancy payout scheme you’d have to do that anyway, if only because users want to see it in a fancy dashboard. So fancy payouts are just added complexity.
Of course pools *should* do payouts in ways that increase payout frequency so that small miners have less outstanding balance with a pool at any time, but making shares ecash tokens is substantially overkill.
