I just bought my Note Air today.
On all the reviews & videos I've seen, all of them say the new pen can be attached to the side. I haven't come across any mention of a Note Air version without magnets to hold the pen.
If we take a look at the page
https://shop.boox.com/products/onyx-...36801915846819, it also says this in the page text:
"The Magnetic function only companion to the Note Air,Not applicable to Max Lumi, Max3, Max2, Note3, Note2, Note Pro, Note, Nova3, Nova2, Nova pro, etc."
So I believe the differentiation is that Note Air is magnetic, so you should buy the magnetic pen, otherwise you won't be able to stick it on the side. If you're buying any other Boox eReader device, then then it won't have the magnet to hold the pen, so there's no point & in that case its better to buy the non-magnetic version. In fact for non-Note Air devices, since they're not designed with magnet from scratch an additional magnet may interfere with normal functionality.
Just my $0.02.
Thanks,
Jp