The e-mail engineering reports are not intended to replace tech log entries, and they are not "unofficial". They are sent to ensure that any entries that have may been made are made known to the company asap so that arrangements for rectification can be put in place in advance - and they are a required, documented, part of the post-flight reporting procedure. They also serve to ensure that something unfortunate happens to the aircraft there is a full record, in one place, of any log entries that have recently been made.
LEA are not alone in this practice, which is not illegal. I have worked for quite a few operators over the years, and without exception crews were required to let Ops know, by some means or other, if there were any snags in addition to formally writing it up in the log.
Any system can be abused. I do not suggest that this is the case here; it is simply a fact.