They might have been talking about erithiol (not sure of spelling) which is the best of them, but barely anything is made with it. Most products are made with maltitol which is a byproduct of high fructose corn syrup and has a very high GI - have a google of polyols and GI - they all have different counts, some better and some worse. Sadly the ones used in most low carb sweets are the worst ones.
Here's one link:
http://lowcarbdiets.about.com/od/nutrition/a/maltitol.htm
Splenda, stevia, xylitol and erithiol are the only sweeteners that don't spike me, maltitol gives many many people problems with BG and can also mess up low carb weight loss attpts.