na.action does not return na.action element of lm object

I'm not sure if this is the official behavior but I would expect the
na.action function applied to a lm object to return the na.action.
Here is what I mean.

x<-0:10
y<-x+rnorm(10)

Warning message:
In x + rnorm(10) :
 longer object length is not a multiple of shorter object length

y[5]<-NA
m<-lm(y~x)
m$na.action

5
5
attr(,"class")
[1] "omit"

na.action(m)

NULL

I would expect na.action(m) to return m$na.action.  This is simple
enough to fix with
na.action.lm<-function(object,...)object$na.action
but I would expect that this would already be included in the base.
Is there a reason that it is not?  I did a search through the archives
but did not turn up anything relevant.

Thanks,
Andrew Redd