RE: Does 5.1 absolutely require TH?

<blockquote>
Does 5.1 require *adding* TH?
(Yes, I understand 5.1 requires that TH be used *in place of* TD where
appropriate, but what about the situation where there is no TD in the
first place?)
</blockquote>

I'm not sure I understand.  If there is no <td> in the first place then
presumably the <table> markup doesn't validate.  Or are you asking
whether it's 5.1 requires use of a data table to provide information
such as name, phone number, office number, etc.?  The answer to that one
is surely no-- there are lots of ways to present that sort of
information.  But if you *do* use a table there has to be at least one
<td> element in it...