I think these days, LOC is a reasonable metric for a peer-reviewed code base. It is unlikely that the lines of code in a given project can be reduced by 10X in a maintainable way. Can we easily reduce the LOC in the Linux kernel or Postgres by 10X for example? It seems unlikely.

LOC is a fuzzy proxy for the amount information in a code base. It should never be used for any kind of productivity metric however since that is obviously dumb and easily gameable (win by writing terrible code). Of course most productivity metrics are fall into the dumb/gameable category so lets not use them.