The short answer is no. An AWS linked account that's tied to a healthy payer can not be removed.
The reasoning behind this is that the payer account CUR, which we collect multiple times a day, includes the linked account line items. The platform system sees these line items and re-imports the accounts if they were deleted.
If you would like to exclude accounts from AWS end so that no usage gets collected on the platform for these linked accounts the only option is to configure the customer tenant through PGB and exclude those accounts from PGB block assignment.