Subsequent Here Doc/String Never Evaluated in Process Substitution

[admin]

Thank you for the awesome shell.  I noticed the following after upgrading  
from 5.1.16-3 to 5.2.2-2 on Fedora.  It actually resulted in a minor amount  
of data loss.
#!/usr/bin/env -S bash --
mapfile -t < <(
        cat <<- EOF
        ;FFMETADATA1
        EOF
        while read -r ; do
                uS='Comment out this line to untrigger the bug.'
                cat <<- EOF
                See?
                EOF
        done <<< 'ASDF'
)
printf '%s\n' "${MAPFILE[@]}"