Edit: It actually did change, I thought the patch note meant that the turn off and turn on sounds were changed to be the exact same sound event. In fact, it was changed to use one sound file rather than two, with the "turn off" sound just being a pitched down version. My mistake!

In the patch notes for 24w19a, a line reads, "Replaced turn off and turn on sounds for Copper Bulb with one toggle sound." However, open using the copper bulb in this snapshot, it still uses the same, distinct turn off and turn on sound effects observed in 24w18a and prior.

Looking through the sound indexes, a "copper_bulb/toggle.ogg" can be seen and heard in the game's files, which is just a renamed "copper_bulb/turn_on." In game however, the command, /playsound minecraft:block.copper_bulb.toggle does not work, nor does the sound exist in game; it will not play any sound nor subtitle.