Yes, cld hear the PSU, so add a dummy load resister to drain 10% full-load?
Is there any real concern if operate the whinning PSU very low load for long term, likely to cause failure?
No, I don't think it will be a problem for the PSU. However, there might problems associated with the response of the PSU to rapid changes in current demand. Voltage dips and overshoots that are not within specification. I can't quantify them; best measured if possible.