I noticed that on the 'browse all entities" - no idea about the internals on how these guys from basis did back when vlisp was vital lisp.
But anyway, my method that uses the acdbCurDwg()->currentSpaceId() or current space will work better since it will grab the entities on the desired location and also avoiding the use of COM or activex extensions as those from all the vlax-XXXX
There are VLAX- methods for active layout or to get by layout name, too.
But do not know if any of those VLAX- calls are faster or not than the (ssget "_X") all depends in the case you are working.... the ssget "x" will get all, but maybe it will be a need to sort out entities.... difficult to say.
My 0.2 cts....