Difference between setting colorloop effect in light state vs group action

Firmware 0x26720700

I’ve been trying to set the colorloop effect on a group of lights through HA, but so far I haven’t been able to do so. So I’ve played around a bit with the REST-API and I’m noticing the following behaviour.

Turning on a group of lights and setting the effect to colorloop in the same REST-API call doesn’t work. The lights just turn on with the effect set to “none”. But if I then do another call and omit the “on”: true field from the data, then the colorloop is active.

If I do the same, but now changing the state of a light, it works immediately in a single call.

So the reason why I can’t get it working in HA is because I’m using groups there (and HA always sets the “on” field I think), but now I’m wondering if there might be a configuration issue in my setup. Or is this behaviour by design?

PUT SERVER:80/api/KEY/groups/ID/action
“on”: true,
“effect”: “colorloop”,
“colorloopspeed”: 15,
“sat”: 255
=> doesn’t work, lights just turn on without colorloop. Remove the “on”: true and send again, colorloop works.
=> apply the same data to a set light state call and the colorloop works as well, even if the light was off before.