Humbe Bundle Store Region Lock

So recently I bought a game from the Humble Bundle Store and made a giveaway for it:
👉 Mega Man X Legacy Collection 2

At first, I planned to review the key and send it directly.
Then I realized the game has a region lock — so I redeemed it myself, and it turned out to be a SEA key.

After that, I did some research and found out Humble offers a giftable link option at checkout.
I tried it — no region lock warning, nothing at all.

However, when the giveaway winner (from Canada) tried to claim the game through that link, he got this error:

“Sorry, but this product is not available for purchase in this country. Your product key has not been redeemed.”

Like… what the heck?
The store should warn about that during checkout, right?
(Especially since bundles and Choice pages do show region restrictions when clicking Create Gift Link.)

I even found a similar issue here:
🔗 Reddit - Why is it always region locked?

From what I can tell, I initially thought the gift link would generate a key based on the receiver’s region — but apparently, it doesn’t.

So, I’m curious:
How do you guys check whether a Humble key is global or region-locked before buying?
Are keys from the Humble Store usually global, or are only some games like that?