Premiums not decaying intraday on non expiry days after 1 Sep 2025

F&O
1

The month where Nifty expiry is switched with Sensex and the average decay just stopped on the option premiums intraday on non expiry days.

Please help me understanding what could be the reason for this.

Thanks

2

Lately the intraday CTM decay is less because sellers are not willing to carry risk overnight without fat premiums.

3

sounds reasonable

but why after 1 sep 2025 , after expiry switched