Yea well, synthetics are not really in their infancy if you take the failed attempt of the 1950's, I think, to popularize nylon knots. That did nothing to help that class of knot and people have long memories. It has been just recently that the idea of a useful synthetic knot has taken hold and a fair effort has been put into improving the class in a relatively short time has been made.
I think they are already able to stand on their own as compared to badger, boar or horse hair knot offering a useful but different set of characteristics from the others. The downfall of synthetics is the constant comparison to badger rather than recognizing and accepting the different attributes they offer. After all, if you want what a badger, boar or horse hair brush has to offer you buy one of them. You don't/shouldn't expect the same performance from a badger as opposed to a boar, they are different.
Yea, you certainly can sling lather with most synthetics if you are an enthusiastic user of painting strokes to apply your lather with. As you say they tend to be springy by nature and most factory lofts are set too high for my tastes making sling lather all the more likely as with a floppy badger silver tip. I have had most of my synthetics reset to lower lofts and face lather using circular strokes to build the lather and painting strokes spread it. I did this after using the very low lofted Chubby2 synthetic and finding it great for face lathering with slinging the lather around. With the Plisson OTH you can almost "crack the whip" with it and will most assuredly sling lather if you get carried away painting with it.
Bob