The amendment is not retroactive, meaning it only applies to children born after it is officially implemented. For children born before the amendment, the only available route remains Article 15(2) (Borang B). So, regardless of the amendment, your child is not eligible for automatic citizenship because the amendment does not apply to children born before its enactment.
Since you submitted your Borang B application before your child turned 21, your application is still valid, even if your child is now over 21. You should continue to follow up on the status of your application. The government promised to process citizenship application within a year.
Continue to keep in touch with KDN officials and track your application through the SSPK portal.