std::is_trivially_default_constructible and volatile types

Looking at the answer to this question:

std::is_trivially_copyable - Why are volatile scalar types not trivially copyable?

I see that the standard says a type is not trivially copyable if it has a volatile member, even when that member is a basic type. This appears to be due to a need to ensure that volatile members are updated atomically, and the byte-by-byte copy implied by trivial copyability can be violated.

But doesn't this also imply that is_trivially_default_constructible should fail on these types?

It seems that this is the correct check to see if a class can "correctly" be zero initialized (memset-able) in the same way is-trivially-copyable is used to detect memcpy-ability. And the memset may be non-atomic for the same basic reason.

However maybe this assumption is wrong. Is it incorrect to assume that a trivially constructible class is memset-initializable? If it is incorrect, what is the correct check to determine this?