Language in the reference guide states, "the calculations must include all restroom fixtures necessary to meet the occupant's needs (toilets, urinals, lavatories, and showers) when seeking LTc4: Transportation Demand Management, Option 2. Active Travel Facilities, Path 2. Shower and Changing Facilities.
GBCI has confirmed that showers should be included in the prerequisite and credit calculations regardless of which other credits are pursued.
Please post if you learn differently from a v5 LEED review report.
Thanks!