One potential issue would be for those who use their HRP (Home Return Permit) to enter Mainland China.

Name on HRP:
陈小明
Chan, Siu Ming

Name on Ticket:
CHAN/SIU = Maybe NOT ok to fly as the person's name in this case would be just "陈小" as opposed to "陈小明".

Also, I think they are more likely to give westerners and ABC/BBC/CBCs (who have their English name as their genuine "First Name" [英文名行先] as opposed to their HK born counterparts where their English name is their middle name [中文名行先]) a blind eye and let them board.

Westerner:
Last Name: Smith
Given Names: John David Jacob Micheal Peter III

Ticket: SMITH/JOHN = OK to Fly

ABC/BBC/CBC:
Last Name: Chan
Given Names: John Some-Thing
Note: [英文名行先]

Ticket: CHAN/JOHN = OK to Fly.