I think you've got that mixed up YB? Surely you mean high ceiling could be amazing, and low floor could be a flop.High floor could be amazing, low ceiling could be a flop. Classic example Bilel Mohsni. Best case scenario with those raw attributes he'd develop into a premiership player, but when we signed him there was also quite a strong possibility that he'd be Rymans Premier at best.
Low ceiling, high floor you know what you are getting.
The four we've signed have high floors as we know they are league two players - even if they don't work out here they'll find another league two club, maybe at worse a conference side and get games with them. But they probably have quite low ceilings given that they have been playing professional football for quite a few years around this level and improvement tends to tail off for most positions by that age. League One might be their absolute peak as a player and they may not reach that peak.
I see it like this:
I think that's what the low/high ceiling/floor thing means.