The only real thing you need to look for is actual gouging of the slide or slide rails. As the rep stated, some wear of the finish does and will happen. Nothing to really worry about. Now if there were gouge marks, I would be concerned. But all the wear you have is normal to any Sig that I have (all 6 at current count).
Slide glide is great, but does come in 3 formulations to take into account temperature. Right now it does make things a bit slower to cycle in the cold we have. But I did not buy the winter mixture. Small tub that I bought should last me for years to come. You can find it on Brian Enos' web site. It's his product. I only use it on the slide and rail contact points. No need to use it where oil will do it job just fine.