Valid markup is not a guarantee of accessibility by itself, although it's part of it. Using appropriate markup is even more important. HTML is primarily used to structure the content semantically (not to format it), so each type of data has to be marked up according to its nature.
In this case, the problem is not the template. The default template for template::list produces valid and appropriate markup for tabular data. Using a table to format a form is acceptable from the accessibility perspective (as long as a few rules are followed), but not recommended. The problem here would be to mix the two types of content: the data and the form to modify it.
