Sorry that it took a while, but I can also confirm success with Xiaomi/Aqara devices staying connected via the Trådfri outlet.
While a couple of my Sengled Element Classic bulbs switched over on their own, in the past two weeksI did not once see any of my Xiaomi/Aqara devices move their connection over to the Trådfri outlet on their own accord.
So, I had to do the same as @SmartHomePrimer to "force" my Xiaomi/Aqara devices to use the Trådfri outlet as a repeater: reset and manual re-join (i.e., don't delete the device from the Hubitat's device list; just start "discover Zigbee & Z-Wave devices" mode, and go through the Xiaomi/Aqara device's pairing steps.)
Rated at 1800W/15A max output according to the manual, these are a total no-brainer at $10 (assuming you don't mind the size/design and the audible toggle breaker 'click' sound)!
