Not exactly. It just means that you should buy a spare battery at the time you buy the phone. Then they can ship outside USA.
Also, in your case, there may be a workaround since land shipment may be possible. Most of the restrictions arise from air shipment.
That is more great news. Things are looking really good. The package arrived Wednesday morning - 3 days ahead of schedule. Saturday, Jim & I go and get a sim and optional storage and start practicing not leaving it laying about 
Fun days ahead
~s
I did a test and added to my cart, “Librem 5 (Evergreen) Battery × 1”
I would go as far as discovering how it would be shipped, I selected Canada, Province and other data.
I did a see a post here https://shop.puri.sm/shop/librem-5-evergreen-battery/ that order would be cancelled and refunded.
SUMMARY:
Not sure how to get a second battery.
Learned a great deal in last few days. My head hurts.
~s
a) You’ll probably have to discuss directly with Purism.
b) Planning any trips to California any time soon? 