As the client set the meeting time and you are running an international team
YANBU
Yes, we all offer flexibility around core hours (formally defined or not) but employees are expected to put in the extra effort when needed.
Flexibility is a two way street.
I used to run a team across several time zones and couldn’t care less what hours people were working so long as they got their work done.
However, when occasion demanded it, and with notice, I would absolutely expect my team to work early or late.
We we’re coming in at 7 for 3 hour meetings so the Shanghai team weren’t in their pjs. West coast teams in at crack of dawn for meetings with European teams etc. etc. 9 am isn’t exactly extreme.
I would say though, if a very hardworking team member who normally would put themselves out if needed, really was struggling (for childcare or some other genuine reason) , I would make allowances (let them come later, if not critical to first 20 min).
I’m sounds like your back is up
and I wonder if this team member has been taking the piss or thinks the rules don’t apply to them whilst everyone else follows a process (making formal request to flex working hours and has this contracted)??