I've been the Workshops Chairman of one of my quilt guilds since January and avoiding what you mention is one of the main goals of my teaching. Start the students with something small (from 28x28 to 42x42) to (1) get the technique and (2) be able to finish it quickly after the workshop is over. I select patterns that either have varying sizes included - in a few cases, this called for my creating yardage charts for same block/different size, so that the student could chose the size they were most comfortable working with at their current skill level. Since the patterns I select are also stash-busters, students shouldn't be too out-of-pocket, if at all. When I send out the e-flyer advertising a workshop, I also post photos of the same quilt in different colorways (which almost always makes each of them look like completely different quilts), and as often as possible, photos of the quilt with some individual flair of embellishments, creative borders, and other unique design elements. The main point of my teaching is "see all the things you can do with this pattern?" in a scale that's "UFO-proof" without large cash outlays.
The instructors you speak of need to be "dinged" in a frank conversation with the management who hired her in the first place. Many times we just don't speak up and this kind of "waste" continues. And, truth be told, sometimes nothing can be done because the management is buddies with the instructor. SAY SOMETHING ANYWAY, and keep looking for workshops elsewhere! If there are other guilds in your area, consider joining them after a few visits to meetings to get better instruction. Never "settle" or truncate your own skills growth by letting deficient instructors discourage you. Good luck!