Expected type(s) for email should include URL

The expected type for the property "email" [1], used on the types
Organization, Person and ContactPoint, is text.

However, an email address is as often as not expressed as a
mailto:address.  And, in fact, almost all of the
schema.org microdata examples that include this property express it as a
URL, such as this example for Person [2]:

<a href="mailto:jane-doe@xyz.edu" itemprop="email">jane-doe@xyz.edu</a>

Google's Structured Data Testing Tool [3] does not complain if the Person
example is run through it, but Google's Schema Validator [4] returns this
warning - as it should, as per the spec:

The property http://schema.org/email expects a value of type Text

Note that it's perfectly possible for a page to legitimately use something
other than text for the hyperlink anchor:

<a href="mailto:jane-doe@xyz.edu" itemprop="email"><img
src="gigantic-email-me-now-button.jpg"></a>

Given this, doesn't it make sense to have the expected types for email to
be set to "Text or URL", as with (for example) the property "menu"?

[1] http://schema.org/email
[2] http://scheam.org/Person
[3] http://www.google.com/webmasters/tools/richsnippets
[4] https://developers.google.com/gmail/schemas/testing-your-schema
[5] http://schema.org/menu