Why would a company be motivated to bring back furloughees if they did not have to? Higher pay scale in many cases (don't know flex's policy) and possible bad feelings for being let go are just the tip of the iceberg. Either a CBA or worry about pilot moral are the only things I can think of. The re interview gives them an excuse to eliminate the problem while looking like they are being fair.

Because bringing back former employees that know the pax, know the proceedures, know how to "do" fractional flying, and that are a known quantity with regard to training performance, personality, and cockpit demeanor is universally accepted in this industry as a good thing.

If they were a problem in the sim, the cockpit, or the hotel van, they should have already been filtered out. Wasting the time and money to reinterview them and discover that their credit score might have dropped while unemployed is just plain dumb.

Recall is always the right thing to do, if a company wants to have a positive reputation and attract quality employees.
Furthermore it reduces training cost and maintains corporate culture.
Performance and morale suffer greatly otherwise.
Unfortunately not all companies care about any of the above...
Best of luck to all you guys.
I feel for you.