If Brad Hand isn't even worth $10 million to a single team in MLB, I am not convinced there is going to be a three-year deal out there for Didi, or even a one-year raise over his 2020 salary. In the current climate, with salaries still possibly prorated this season and the uncertainly of a labor stoppage/lockout in 2021 added in, the fact that it might be even harder for Didi to get a deal after 2021 is all the more reason for him to just take the QO.
And the Phillies don't want him to do that, unless they're ready to concede they aren't keeping JT. This isn't like 2017 when they had a ton of money and CBT tax room, right now they have neither.
They should try to sign him him a two-year deal, with little or no raise, before the QO deadline even comes. But I assume players are't going to be ready to wave that white flag too early in the off-season. Some will come to regret that.