Did not know this, but I found in a topic that a hue bridge is indeed required. I also hoped it was not necessary, however I do see the advantage of the bridge for firmware updates of the devices itself.
Topic: [Info] Homey - Homey Bridge - Homey Pro Maximums / Limitations - #4 by Oritel
It states:
The Philips Hue App for Homey requires the Philips Hue Bridge. It is possible to use more than one bridge on Homey Pro (local) but maximum of one Hue Bridge in Homey (Cloud)
