Thing is, when you sell a module there is an existing option to 'buy back' sold items. So, even if someone sold the core module, they couldn't leave the station without it installed, and would be able to simply buy back the sold item - thus, no problems.
That option isn't available once you relog and I'm not sure it's even available once you leave the outfitting screen and return, I haven't tested that.
The instance I refer to in my post was about a player selling his landing suite module, which can be sold, and logging out. When he logged back in he was unable to leave the station because it was within the exclusion zone for non horizon players, so because he didn't have a landing suite he couldn't leave the station, the station didn't sell landing suites and there was no buyack option because he had logged out.
I can easily see players ending up at a station at the end of a play session and changing some modules, selling others and deciding to finish when they next log on, only to find no FSD large enough to get them to the next system, not having a buyback for the one they sold and not having any in storage they can get sent to them. You don't atually lose any lose money with the current system, but some players think it's slight inconvenience, but it could be a major issue for FDEV if they start getting a flood of support tickets, so why not leave it as it is?