I can confirm that it definitely happens every boot up.
Didn't care much but it's pretty interesting that this was an unknown issue.
MT3000 also has similar symptoms, but at least seems it's known to the devs.
It takes longer than average, but felt it's normal. I've never ever seen any other vendor provide that plenty of features into a such low-end hardware and supports this long.
And TP-Link ER series which also based on OpenWrt take significantly longer boot up time, so I didn't felt it's unusual.