Answer
Correct — Custom Columns don't propagate their visibility/layout through the Base Profile the way Custom Fields do; this is a real, confirmed difference in behavior between the two, not a configuration mistake. The working alternative: configure the custom column's visibility, size, and position exactly as needed on one reference account's own session, save that as a Personal Profile, export it, and then import that same Personal Profile onto each target user's or terminal's account — this reliably deploys the correct custom-column layout, which the Base Profile alone can't do for this particular kind of customization.