[CSS2.1] Table height algorithms and vertical-align <length>

Neither the CSS2 or the CSS2.1 specifications address vertical-align
<length> in section 17.5.3 Table height Algorithms.

Is there a reason for omitting <length> and <percentage>?  If so, CSS2.1
should state why these values of vertical-align are not appropriate.

If this is a oversight, I think the spec should say that they have their
meanings as defined.

Jim