I don't think you need to but I don't see why not you can remove your device entry in your list of Device before changing the motherboard. I have replaced a motherboard before and I didn't remove pc in Device beforehand.
Prior to account linking i changed motherboard and could not activate windows 10 using my windows 7 key, had to have an MS tech remotely mess about in my PC and he couldnt make my windows key work either and ended up just giving me a new one instead. Not looking forward to next mobo change.
This is more or less my experience. Despite the 10 key now being a digital licence I could view online, trying to activate it via my account using the significant hardware change wizard in Windows failed. I tried ringing Microsoft and they asked if I had the Windows key I upgraded from. I didn't have it to hand so I rang off. Eventually I found the Windows 8 key that I received via email when I upgraded from 7 to 8. I thought I'd try entering it myself and it activated no problems.
Umm, my dually xeon board activates windows 10 automatically, so probably from my windows 7 key, my current rig is also activated from when the tech had to give me a new number when he couldnt make it activate on my windows 7 key. so now i have two activated. I'm hoping i can just activate my new build on my linked account (the tech given key) and still retain my windows 7 key as well.
Looks like I'm going to have some fun when I build my new pc! Luckily I still have the retail boxes for my Win7 discs.
I have just been through this having bought a load of new drives and decided to do a bit of hard disc merry go around on my machines pushing big ones from my main machine down to laptops etc, in the process I managed to loose my win 10 license on one machine, could see it digitally but could not select it, called MS, they kept asking for an old key etc which I did not have, didn't think i needed it, it's all digital after all, went around in circles with tech support searching my bios for key etc but its built not bought, so not there, in the end they just gave me a new win 10 pro retail key, after I showed proof of buying new drives etc. So it can be a pain but persevere.