I use FL10 to slow down on the glide if FL5 is struggling. It works because it does add some drag. I don't use it often but it is well known that FL10, speedbrake and 180 kts gives a very good, controlled ROD.
I've also seen lots of other pilots using FL10 on the glide and it's taught in line training. Our airline (second biggest operator of the 738NG worldwide) prefers it to the use of the gear beyond 5d.
Too many pilots believe there is only one way (their way) of flying the aeroplane and can't tolerate or understand other approaches to resolving a problem, but I believe it's always worth listening and learning from others, be it a 10,000 hr Captain or 200 hr cadet.