in-Steam gifts and region lock

To avoid possible miscommunication, let me be clear that this is on top of checking the aforementioned 10% [always round up, to avoid issues with short-term fluctuations], which SteamDB thankfully makes rather easy to do.

My previous comment was specifically responding to the error message the OP had brought up, with the error message for regional pricing instead being "Due to regional price differences, the gift you are trying to send cannot be sent to the recipient's region."

My personal experiences conflict with that, and every single Google'd result I found explicitly declares that as being an impossibility, with directed remarks towards the necessity of VPN for the activation. Obviously, this isn't to contradict your assertion (that doesn't seem like the kind of thing you'd confuse a recollection of, after all), but until we can get some more supporting comments to help us work out a different explanation, it's easiest to assume your experience was due to a bug (which, with Steam being Steam, isn't exactly unlikely).

Rather, out of the couple hundred comments on the matter I went through on Steam forum threads, Reddit, and info sites (including more formal ones, like StackExchange), the only one I found that even implied a possible exception was here on SG, and even it stated that it shouldn't possibly for properly configured licenses: https://www.steamgifts.com/go/comment/JTnau22 . It did, however, state a similar process of a 90 day delay for keys not needing a VPN, so that would certainly seem to support your own experience.

One possible- but very uncertain, very out-there guess- is that you maybe didn't actually get a region locked/restricted/etc key, persay.

Instead, it could be something really specific, like getting a localized key- that is, a completely different release of the game that was formatted for a specific region; For example, this instead of this- and having it configured so that it's activatable in any region, but having Steam automatically assume a launch delay as necessary for it, due to how it's configured to be sold. Put another way, perhaps the exception comes about in a circumstance where the game is the thing changing regions, rather than the Steam account being the thing doing so.

Or, maybe it's one of those weird backend quirk configurations, like how some free games drop trading cards despite their not being supposed to. Or, again, maybe it's just a bug- really can't put that possibility aside too easily, with Steam.