Reshoots are currently under way, with Ben Affleck, Ray Fisher and Amber Heard back as Batman, Cyborg and Mera, though Henry Cavill's Superman is noticeably absent from the cast list for the big-budget `reshoots.`
Leto's Joker did not appear in 2017's Justice League and to the best of my knowledge, was never supposed to, even when Snyder was at the helm before Joss Whedon took over. That makes Snyder's series sound less like a `reshoot` than an opportunity to introduce new material and placate an Oscar-winning actor who was miffed that much of his performance in Suicide Squad was left on the cutting room floor.
Leto has been quite vocal about his desire to return to the DC Universe, and he stars alongside Denzel Washington and Rami Malek in WB's upcoming serial killer thriller The Little Things, so perhaps the studio saw an opportunity to keep him happy - or maybe Snyder was just a big fan of what Leto brought to the character. I certainly didn't mind his performance in the mostly wretched Suicide Squad, but it was definitely a choice.