Steel barcelets for Submariner date

[Burrost1]

Hi, just joined the forum and have a quick questions, I have owned many different Rolexes over the years and after an brief hiatus have just got back into buying them, i've just picked up a 1991 Rolex Sub date in mint nick and when having the strap altered the guy at the jeweller mentioned that the strap felt a little light. My question is has the strap changed from the 1991 to become slightly heavier (or better quality) over the years? This is the oldest model I have owned. The watch is 100% legit but I am now doubting the strap!!
Thanks