No, "Official" is sanctioned by GTP and run by approved staff members of

such as the WRS. It is run properly to strictly enforced guidelines and will be picked up by another organiser (or the burden shared) if one staff member cannot run it by themselves. It will not be abandoned.
It will be run with a view to being all-inclusive, there'll be some of each kind of car and track, but it won't be restricted to only NASCAR or only JGTC.
Unofficial is anything else run by normal users, which can have very different guidelines and is not

's obligation to enforce. These series frequently pop up, generate a little interest and sometimes run to completion and are sometimes abandoned mid-way through.
Laptime challenges like the Nurburgring or Suzuka challenges are not necessarily "series", but they're not "Official" GTP events either.
If you, for example, wanted to run a JGTC event using only JGTC cars and tracks featured in the JGTC series, then that's fine, it'll belong in the Long Or Short Race Series subfora depending on the number of races, but it'll be your sole responsibility to maintain the series, races, results, etc. and will not be posted in the WRS area which is reserved for the official GTP sanctioned events, just as has been done with GT3, GT4 & GT5

events that've been run (successfully in many cases) such as ARCAT, GTPCTC, GTPLMS etc.