I have been following Billy Gibbons a long time having grown up not far from Houston in the 60s where the Moving Sidewalks frequently played around. Hendrix had good things to say about Billy. Most rock guitarists improvise when they solo. I copy signature riffs but improvise extensively which is what the artists themselves do when they play live
I remember those days as well - and was in high school in the 60s.
Allens Landing, Love Street Light Circus, Texas Opry House, The Catacombs, all of that.
I listened to Country as a primary staple of my music, but ZZ Top (in the 70s), Johnny and Edgar Winter (also 70s), Gatemouth Brown, Rocky Hill and others always caught my attention.
Those were the days.
Yes, after playing a song a thousand times they DO improvise or change the arrangement, as do cover bands. You heard them when Hendrix was still alive? Wow. Didn't even know he was of age at that time.
I'll ask you also: What was on the inside of the double album of Tres Hombres? It always cracked me up. BTW, I've seen and enjoyed their straight up blues/rock many times. Still listen to them. Just simple rock n roll and blues. I started with the Allman Brothers Band.
Another fun fact: I took my wife to see them here in OC back in the early 2000's. Skynard openrd for Top and blew them away. The wife (and I) were disappointed with TOP at that concert, but she has since become a life long fan of Skynard.