Do reviews happen more in Holiday season?
Reviewers set their own schedule subject, more or less, to deadlines set by the editor. Some might use holidays to work on reviews. Others might rather avoid anything that looks like work. The "end of January" may be a guess or may be more firm, depending on the deadline request sent to reviewers. Perhaps a reviewer has made a "promise" to be done by then. 

And what is "expected" may not come to pass since reviewers aren't employees, but volunteers.