Logically, if the BB shell was twisted, the chainrings would still run true (no wobble).
Chainrings not running true would be attributable to 4 things (or a combination):
- Bent bottom bracket spindle
- Bent Crankset/Chainring spider
- Bent chainrings
- Crankset/bottom bracket interface not perfectly in alignment.
For vintage chainrings, it used to be common to true them slightly after installation. I'm not quite sure why it was necessary, but perhaps it had to do with the design and manufacturing of square taper cranksets not getting everything perfectly aligned.
After installation, mechanics would just take an adjustable wrench (or similar) and bend the chainrings slightly to align them.