I am afraid it was strength progress, sorry for the vagueness.
Thus I have no pictures to prove, from personal experience I had good strength progressions with Bill Starr 5x5. I added about 30kg to squat, about 20kg to bench and about 40-50kg to deadlift in 12 weeks.
I am currently on week 5 of this program. It’s good stuff.
You will get stronger, and even if you don’t reach your physique goals, it is only a 12-week program. It’s 3 months of your life. No need to overthink it, just do it. That’s the only way you’ll know if it works.