Triac On state minimal Current
When you maintain IGT at 5mA or higher continuously, the triac will stay on all the time, as the PN junction is still in ON mode. IH is only valid in the context of a triac working without IGT anymore.

On a side note, I recommend you use more than 5mA, because this is the current for 25 Celsius. Below this ambient temperature, you need to trigger with a higher current. I recommend you use 10mA for a 5mA triac.

I hope this helps.