Both things are interlinked and there is always a reason why extension is given. Since Income Tax Audit filing is extended, the financials will be prepared after 30th September. But last date of AGM is still 30th September, 2021, hence they can not put date before the date of AGM as they only have 15days of time for UDIN generation.
This issues can be solved by two ways.
1. If they extend UDIN relaxation (which they have done), even if Audit is completed after 30th Sep, they can still put a date of Balancesheet before 30th Sep (i.e. date of AGM)
2. by Extending AGM
For MCA, it is easier to given instruction to ICAI to relax UDIN requirements than to extend AGM as AGM has impact on many provisions. MCA will always go for easier option.
AGM has never been extended except in 2020 because of pandemic. Trust me, they will never extend AGM. However, if they does, then best for us.