Very likely this is to avoid US sanctions.
It just seems weird to me; have we heard reports that other brands (even US brands) of Android phones have been soft-bricking themselves if brought to disallowed countries?
Even state-owned companies like ZTE were hit seriously after sanction. They admit they only did the violation because they underestimated the enforcement.
Companies get so careful is because themselves could be sacrificed as political bargains.
Trying to render "grey" market as something bad is a trick of brands.
Anything illegal is automatically black market, as that is the definition of black market.
But as a manufacturer, we have to get regulatory compliance for our products from the countries we sell to.
Yes, this is a Big and Expensive deal.
Of course, a grey marketer can physically ship our products from one regulatory regime to another without our permission.
So a countries regulatory authority finds our product for sale in their country and it doesn't comply with the regulations.... what recourse do they have?
The most common one is confiscation from the sellers.
But if the problem is sufficiently widespread, they may choose to put pressure on the manufacturer.... do something about this or we will block the sale of your goods in our country.