Here is what I would recommend regarding language use in a schedule (and this is the recommendation in Eric’s book – Forecast Scheduling)
Summary Tasks – if a deliverable – using a noun, eg location, design. If it represents a phase, use the present continuous tense (-ing), eg Researching, Remodelling.
Detail tasks – present tense of the verb – eg design artwork, approve recipe, define standards
Milestones. deliverable and past tense, eg testing completed, recipe formulated.
For my part, using the right language helps remove ambiguity from the the WBS which helps us all, especially when tasks are reviewed in isolation without the rest of the WBS to provide strucutre, as can happen in a filtered view, a report, or in Project Web Access (eg My Tasks).