I always wait for the return to complete processing and any refund received...if the original gets sucked into the errors department for manual processing your amended return wouldnt be able to be matched to anything making it land in error processing as well or maybe even returned as non-processible.

2021 1040X wont be ready for use until the end of February anyhow, so unless this is a prior year amendment, you're still in a holding pattern for awhile.