I *think* the issue is that there may be no immediately available MX cover (at a remote destination say) and the crew may not be authorised/permitted to sign off the log themselves, either by company policy, regulatory edict, or union/demarkation issues.
It's analagous to having a sore, but not painful, tooth on vacation. If its not really bothering you, the hassle of finding a local dentist probably means you'll 'defer' the dental snag until you get home. But if you had a hypochondriac partner, and told them ('put it in the log') you'll be spending the next two days trying to say 'please, not the pliers' in pidgin-swahili or whatever ...
It's something likely trivial to deal with or defer with resources available, but a real bind in the wrong location.