Regardless of what happened on X night, don't count on that happening on Y night.
Even within the same week, different nights can find a different number of guests at any given evening show.
Arriving earlier will cover the more difficult of seating situations.
If seeing a particular performance of a WDW show is IMPORTANT to you,
arriving far too early will beat arriving one minute too late.
OTOH, if seeing a particular performance of a WDW show is only of passing interest,
you can certainly arrive closer to show time and you might be lucky.
Sometimes that works fine.
Other times, not so much.