I haven't seen the ad, but it seems most likely that the kit in question is a reboxing of a Heller 1/150 kit. As we've established before in the Forum, Heller kits have turned up in a bewildering variety of boxes - and Heller boxes have held a bewildering variety of other companies' ship kits. And we know from experience that some, at least, of the people responsible for the printed copy on Revell ship kit boxes have no comprehension of how scale works. Labeling a 1/150-scale kit "1/250" would be utterly consistent with Revell's normal standard of behavior.
If it is indeed the old Heller 1/150 kit, it's a pretty good one. I have two reservations about the Heller Pamir and Passat - one being endemic to the plastic molding process, the other a silly but relatively minor Hellerism.
First, that sort of ship just doesn't lend itself well to reproduction in a plastic kit of reasonable size. Those German schoolships were enormous, and their decks were cluttered with complicated mechanical gadgets. An early-twentieth-century "winjammer" would not be complete, for instance, without its Jarvis brace winches. A reproduction of a Jarvis brace winch on any scale would be a major project; in 1/150 scale it's beyond the capacity of a commercial kit company and the injection-molding process. The Jarvis brace winches in the Heller kits are recognizable; that's probably the best that could reasonably be expected. One doesn't see many well-detailed models of this sort of vessel on any scale; that's one big reason why.
The other problem concerns the yards. Heller molded each yard with a series of little oblong-shaped lumps on one side, to represent (vaguely) the jackstay eyebolts. The modeler was supposed to glue pieces of wire (which, if I remember right, were actually included in the original issues of the kits) onto the lumps to represent the jackstays themselves. Not such a terribly bad idea - but the designers, in one of those irritating Hellerisms, apparently didn't understand what the jackstays were for. Those particular ships probably (I'd have to check photos to be sure) had two jackstays on each yard - one on top, for the sailors to hang onto, and one 45 degrees forward of the top, to which the head of the sail was secured. Heller put the "eyebolts" on the fronts of the yards, where they look utterly ridiculous. Shaving off the little lumps would take all of fifteen minutes - but the modeler would then be confronted with the job of figuring out some other way to represent the jackstays, in the right places.
Otherwise, as I remember the kits (it's been a long time since I've seen one), they were reasonably accurate and well-detailed. They're challenging; a ship like that has an enormous amount of rigging, much of it extremely repetitive and, in the prototype, much of it made out of iron chain. Those kits could be made into pretty impressive scale models. I'm not sure I'd want to tackle them, though.