The chemist in me says we are comparing apples, oranges, yo-yos, and pickup trucks.
Black powder is extremely stable in a wide temperature range, with little to no degradation in power. Damp, it doesn’t like to ignite. Once dried out, you are back in business.
Smokeless powder is not as robust for long term (50+ years) storage, and is subject to chemical breakdown under certain (mostly high temperature) conditions. In the late 1980’s I used powder recovered from corrosive primed 1942 .30 M2 Ball ammo for service rifle competition, and did well with it. I’m also currently working through some similar vintage 4831 with no issues whatsoever.
My personal experience with Pyrodex (powder) is that stored properly (cool and dry), it mimics smokeless in its “storeability”. It will “clump” if exposed to moisture, but as long as your can does not become one “chunk” of Pyrodex, you’re OK. I’ve shot Pyrodex recently given to me that came in the “vintage” cardboard “cans” with no problems.
A friend has had problems with Pyrodex pellets becoming hard to ignite, but I don’t know how well (or not) they were stored. He gave me the remainder of his (unreliable) pellets, and even thrown into a fire, about 30% of them didn’t ignite as quickly, or with the energy as “fresh” pellets. BTW, these came in clear plastic “tubes” no the plastic “cartridge box” type container.