Since upgrading my world from 1.21.4 to 1.21.5 frogs are no longer dropping froglights after consuming a small magma cube.
I have tried with both an existing farm on the nether roof and with frogs and cubes spawned in with blocks. Also tried spawning in via eggs in the overworld
In all instances, magma cubes consumed by a frog do not cause the frog to drop a froglight.
In a fresh 1.21.5 world, I cannot reproduce this behavior.
This can be closed. I still had some old 1.21.4 Vanilla Tweaks datapacks installed. Once I removed those, the frog behavior returned to normal.