I believe the industrial bonus only applied to metropolises.
In Civ3/PTW, everyone got an extra shield when hitting size 7.
I just did a quick test in the debug mode in C3C.
At size 7, all civs get +1 shield BUT there is some confusion here, because you will only 'see' the bonus if you built on a shield tile (bonus grass, plains, desert, etc.). When applying the bonus, the game looks at the base terrain, and if it previously had 0 shields, it adds 1, but that still gives you the minimum 1 shield.
When hitting size 13, all civs got +1 shield, and industrious got +2 shields (+1 more than other civs).