I usually only apply EP to 7"s with 4 songs or more. 3 is kind of ambiguous. Although it looks like the commenter is correct:
6.10. Album, Mini-Album, EP, Maxi-Single and Single tags should only be used where it is factual. If there is no reference that the use of the tag is correct, the tag should not be used. References can include; a) mentioned on the release, b) declared by the label or artist, c) charted in a relevant chart that corresponds to the tag, d) generally regarded as such by independent sources (fan sites, music industry publications etc). Do not guess at or attempt to apply personal standards to these tags. If you are going to do multiple edits regarding these tags, remember to follow guideline 14.1.2.