The internal ID has been kept after a comment by @tjcafferkey. This causes a
bit of inconsistency in the internal code, but it was deemed that it would have
been better as users who have customized templates using this
blocks ID will have saved this in their database, and it would result
in a corrupt block when loaded, and we didn't want to support both IDs at the
moment.
Otherwise, most other references to the legacy template, are now using the word
“classic”.
Co-authored-by: Alba Rincón <alba@albasauatticmbp.home>
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