Brand new Shimano BB-UN300 hard to spin when drive side is fully torqued
It is possible for BB shell distortion from welding to cause excess friction in BB cartridge units. Usually this is accompanied by roughness screwing in one or both parts of the cartridge. In those cases, chasing and facing the shell typically eliminates the issues, and there's not much else that can be done.
What you describe could be the normal friction of a new lower-end cartridge, which will tend to get better in use, or it could be a symptom of the above. Doing a test with a crank as you describe may make it harder to see what's going on, because the crank creates so much leverage. I would install the cartridge in the normal way and then test how freely the spindle turns by hand. A little friction is okay but it shouldn't be much more than that.