Your TAO-XMN flight is purely domestic, regardless of flight number and possibly large aircraft (maybe both a continuation from the long haul). This means you can’t access XMN immigration when arriving from TAO.

Beside the check in counter abroad, when you use TWOV to enter China, the immigration officer will closely examine your ticket and schedule before granting TWOV. It’s not like they’ll just stamp you in for 24 hours. (All stamps appear to just have dates but no time. Maybe that’s why all 72/144 hours count from 00:01.)