@blanchsb thanks for looking into this.
What you say in your first answer is exactly where I was at, although I didn’t explain it that clear as you;)
There is a different dependency graph since 2.8, so I tried something in 2.79 and found that when you ALT+D a Cube (8 verts), the stats say 16 verts (same as if you had SHIFT+D’ed). So there the behavior was more consistent.
Some stats with 2.97: (file sizes of Scene with Monkeys):
With Subsurf on: ALT+D. 530 kB, SHIFT+D. 1.1 MB
Subsurf applied: ALT+D. 1.2 MB. SHIFT+D. 9.5 MB.
Now that is the kind of behavior I would expect!
As to your second post, yes that is strange and sounds also more logical to me….
