To be clear, I'm saying that almost all scrapers and metadata services I've used are writing the release date in TDRC, which is not what the standard specifies ("The TDRC frame is officially to be used for the recording time, TDRL is for the release time").
Correct.
TDRC (v2.4) = TYER (v2.3) = recording time and is "track" based.
TDRL (v2.4) = - (v2.3) = release time and is "product" based.
Example:
You have e.g. a compilation with 70's & 80s bought in 1998,
which includes "Lipps, Inc. - Funkytown" from 1980, "Patrick Hernandez - Born to be alive" (1978)
Until v2.3:
Option 1: In TYER you have stored 1980 for "Funkytown" and 1978 for "Born to be alive".
Option 2: In TYER you have stored 1998.
You could have used TORY for 1998 or 1980/1978, if a software would have supported TORY and people would have stored this information (they most didn't).
Of course it all wasn't clear for everybody.
With v2.4 you are able to store both v2.3 options and id3.org has decided to add the new tag TDRL for v2.3/option 2.
That's why TDRC is TYER(+TDAT+TIME), and TDRL is new.
If people have used option 2 in v2.3, they should clean up their collection for v2.4 and move 1998 from TYER/TDRC to TDRL.
So with v2.4 you have
TDRC with 1980 for "Funkytown" and 1978 for "Born to be alive".
TDRL with 1998 for the product release date (the compilation release date).
Personally I think
"Product release time" is a good name for the column TDRL - and very clear.
"Track release time" is a good name for the column TDRC.
"Original Product release time" good be a good name for TDOR.
Regarding TDOR:
If you have bought MJ - Thriller album re-release from 1996.
TDRC = all tracks have 1982 (if a track would have been released/recorded as a single earlier then there would be another year for this track!).
TDRL = 1996 (= product release time)
TDOR = 1982 (= original product release time)