it is not up to SQ to approve or decide the transit rule.
The Singapore Govt/ministry of health will decide
when there are changes, usually they will give around 48 hours notice. For example, on 10/July, it was announced that Indonesia paxes were not allowed to transit via changi from 12/July 2359hrs.
Any changes are usually due to the worsening of situation
https://www.moh.gov.sg/news-highligh...esia_10Jul2021