Hi
I use the same LCD module with the MIMXRT1170-EVK. [https://www.nxp.com/part/RK055HDMIPI4MA0] and it has the 40 pin connector matching the board.
I think that you are referring to the 31 pin connector on the RK055MHD091A0-CTG (from Rocktech), which is the sub-module used on the expansion board - from NXP.
This photo from the reverse side of the expansion board should clarify.
mjbcswitzerland_0-1770164350616.png
Mine is from 2018 and doesn't have the A0 at the end but the LCD expansion module is designed to work with the EVK (or the EVK to work with it).
Regards
Mark