It depends on your definition of "Conceptual" --
X have feature and
Y not?" is a pretty nearly unanswerable question ("Because Y's developers didn't implement it" is THE answer, but it's a pretty shitty answer, and totally unhelpful). I can't think of a SE site where it would fit because nothing on the network focuses on speculation.
Your question falls into this category as best as I can tell -- the only people who could really answer this are the OpenLDAP developers.
"Where would you use feature?" is an interesting category of conceptual questions -- these really don't fit on Server Fault ("Solution in search of a problem" doesn't work well), but there is value in some of these questions.
Your question almost falls into this category (the second part is "Why would I use this attribute?") -- that's the type of answer you got, and I think it's probably the most useful :)
"I've got these requirements, and I'm considering this architectural solution - Does my idea suck?" is a category of practical conceptual solutions that sometimes works and sometimes doesn't.
These can be really AWFUL "do my work for me!" questions which need to die in a fire, or they can be good, detailed questions asking about specific concerns with a proposed solution which can develop into good resources. The latter definitely belong on Server Fault.