UML22 — Why not using the UML1 activity symbol for UML2 actions?

I didn't recognize it before, but now I am surprised that the action
symbol
is not the same as the UML1 activity symbol ("shape with straight top
and bottom
and with convex arcs on the two sides").
Actions are no activities, but the semantic is similar for
the "normal" UML user.
In UML1 the user has to distinguish between the activity symbol and
the state symbol ("round-cornered rectangle"), especially if states
and activities
are shown within the same diagram.
Now you has to use the UML1 state symbol for actions. I think that
this is confusing
for the normal UML user.
Another point is that the action symbol is the same as the state
symbol. There will
be no chance for a misunderstanding, because both symbols are not
allowed within the same
diagram. But it would be much clearer if the action symbol has a
different notation and
looks like the UML1 activity symbol.

So, why not using the UML1 activity symbol for UML2 actions?

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