Thayer indicates the two derivations of αἵρεσις - heresy - and thus demonstrates the twin meanings of the word. See Biblehub - Strong 139. This noun is used nine times in scripture.
From αἱρέω, the active form of the verb, comes the meaning of 'capture' - for example the storming of a city. This word is never used in scripture.
From ἁιρέομαι, the deponent form, comes the meaning of 'to choose'. Being deponent it is a matter of a response. It is not an active initiative nor is it a non-active passivity : it is a response to something else. This is used three times in scripture.
Someone is influenced by something - and they make a decision regarding it : they choose to align with it or to assimilate it. Its existence draws them to embrace it.
The use of this verb is in sharp distinction to the use of the other verb regarding 'choice' in the bible - εκλεγω, eklego - which is always used in a positive way of an honourable and righteous decision.
In both cases, the verbs indicate a union with what is chosen. One becomes one with what one embraces, is what I understand by the use of the two words within scripture.
Either for good or for evil.
From the two derivations above, noted by Thayer, comes the concept of a tenet that influences a person who, in turn, influences others, resulting in a heresy. The noun, as used in the Greek, means both the heresy that is embraced and also the group who embrace it.
'That which is heretical' can refer to the ideology that is propagated or it can refer to that body of persons who do the propagating. Merely holding the ideology in the mind, makes one part of that body. Just as believing the gospel, from the heart, makes one part of the body of Christ.
Therefore the single use in scripture of the word in question (in the adjective form, the accusative masculine singular) αιρετικοσ - heretic - does indeed, as we see the above translations, noted by the OP, bear both the meaning of being influenced by false teaching and also being the cause of sectarian division.
Thus the English word 'heretic' should be recognised as having two parts to its derivation and therefore two parts to its meaning.
There is only one truth. To voluntarily depart from truth is not only an unrighteous choice in itself, it is also a deliberate attempt (conceptually) to capture what is real (the gospel and the church) and to change it into something unreal.