I think the idea that the Saltire took over as the more common flag rather than the Royal Standard because of a push for Independence shouldn't be exaggerated. I think there were other factors too. Maybe more significant. When I first went to Scotland games in the mid 70s the Lion Rampant was indeed more numerous. But far more folk voted for the SNP in the 74 general election than ever voted for them in the 80s, 90s or even noughties. I think the demise of the Home Internationals and Scotland's opponents then being virtually always non British was maybe more significant plus Scotland's regular qualification for international tournaments when using your nation's flag rather than the Royal Standard became the norm.