The morphosyntactic behavior of Latin deponent verbs differs from that of passive non-deponent verbs for a few non-finite forms/constructions, where deponent verbs are conjugated the same way as active verbs.
According to "Deponent Verbs" from The Latin Library online (William L. Carey), deponent verbs use the same forms as active verbs for the present active participle, the future active participle and the future active infinitive (which is just the future active participle along with "sum").
So, taking sequor as an example, it is possible to distinguish it from a passive verb even without translating it by using the criterion that the present participle form "sequens" has approximately the same meaning as the relative clause "qui sequitur", while the passive of a non-deponent transitive verb has no corresponding present-participle form with the same meaning.
Some derived forms of deponent verbs also pattern like those of active rather than passive verbs: for example, agent nouns in -tor such as secūtor.
The fact that deponent verbs pattern differently in some respects from the passive versions of non-deponent verbs doesn't mean that they can't be grouped together; for comparison, in English, the category of "active verbs" includes verbs of different behavior such as transitive verbs, intransitive verbs like fall that have a past participle that can describe the state of the subject ("a tree that has fallen" ≈ "a fallen tree"), and intransitive verbs like walk that have a past participle that cannot be used to describe the state of the subject ("a student that has walked" ≠ *"a walked student").