GL stands for Geocaching Log - this URL points to the log itself. In the email the cache GC code is a link that points to the cache.
I think the Log URL is correct as the email really talks about the log itself, as can be seen in the three lines immediately above, and not about the cache. And there is a need for a link to the actual log, in case it is formatted in a way that does not translate to the email.
There is a link to the cache already. Although there is a change in the format of the email, there is no fault of loss of data.