I do not work for eBay
nor do I own their stock any longer, I am only offering an alternative perspective.
If anyone was motivated in making the case you state then I assume that they would need to hire a lawyer, open a discussion with the Treasury Department, get them to make a ruling or decision in writing. Then this could be taken to eBay
to see if they would consider change in policy and ultimately their algorithm. Be aware that 'Stamps' (or even Collectibles) are probably not on their radar... eBay
exists to make money for their stockholders, their stockholders want the company to be profitable. I doubt that the stockholders care about a category which is not significant to the bottom line.
I agree that some folks ought to switch to Hipstamp. Dealing with a large corporation is not the same as dealing with a tiny company. (Hip has 15-20 employees compared to eBays 14,000+ employees.) In my opinion expecting eBay
to care (by making exceptions) about a category which accounts for a very small percentage of their income is not realistic.