When there are two onsite stays as
@tjmw2727 explained, the rolling window from Stay#1 rolls and meets up (adjacent) with the new FP window, the new window then opens (day early).
The others with the OP may have tickets as part of a package so they aren’t yet valid until the ‘package’ window opens.
If the others had separately linked tickets, their FPs could have been booked when grouped with the OP.