SES domain identity verification pending for awsapps.com from different region

Our organisation is currently testing an AWS Workmail + SES setup. As AWS Workmail is not available for our region we've set this up in us-east-1. We've created a WorkMail organisation 'abc' (example), with corresponding aws provided domain 'abc.awsapps.com'. The DNS is managed by Route53. The setup completed fine, and the SES domain identity verification process for us-east-1 finished within minutes.

We'd now like to apply SES settings for 'abc.awsapps.com' in other regions (same organisation, different regions). According to AWS documentation, there should be no issues doing this: https://aws.amazon.com/blogs/messaging-and-targeting/how-to-use-domain-with-amazon-ses-in-multiple-accounts-or-regions/ . We're aware different regions have different validation records.

The required set of CNAME records for the other regions were added to the Route53 hosted zone (in fact AWS adds these automatically, so there is no chance of a misconfiguration here. We can see them in the console too). However this time the verification seems stuck in 'pending'. This long wait seems to happen for ANY region other than us-east-1 (incl other us regions).

nslookup cannot find CNAME records other than the ones from us-east-1.

Interestingly,

dig -t NS abc.awsapps.com

shows a different set of name servers than the NS record in Route53. (I've tried updating the NS record to match the server set from dig, but doesn't look like that helped anything....)

Are there hidden restrictions or additional requirements in play here? Why would identity verification be so fast for us-east-1, but keep pending for others? It's been days...