A voice profile is a recording of your own voice that Junior keeps so it can pick you out on the microphone channel and put your name against your speech instead of a generic label. You enroll once, and from then on enrollment is the only control there is — there's no per-call setting to turn matching on or off.
Once you have a profile
Matching runs on every call you start. That includes starts that don't show you the consent dialog at all, so you don't have to do anything at the start of a call to get it.
When the consent dialog does appear, it tells you that voice matching is on for this call. It's a statement, not a choice — the checkbox that used to sit there has gone, because the profile already answers the question.
If you haven't enrolled
You'll see nothing about voice profiling in the consent dialog, and Junior won't try to match anyone's voice on the call. Speakers get labelled the ordinary way, and you can rename and merge them afterwards.
Enrolling
Look for voice profile enrollment in Junior's settings. The flow ends with a save step, and the profile only counts once you've saved it. Enrollment is available on both Mac and Windows.
Enrolling in the middle of a call
Whether matching is on is decided when the call starts and doesn't change while the call runs. So if you enroll halfway through a recording, that recording won't get matching — the next one will. If you want a call matched, enroll before you start it.
The same goes the other way: a call that started with matching on keeps it for its whole length.
To check: I haven't seen the running app, so the wording in the consent dialog and the exact place enrollment lives in settings both need confirming — this page deliberately describes them rather than naming them. Worth checking too whether enrollment is reached from settings at all rather than from somewhere else, what the save step is actually called, and whether deleting a profile turns matching off for calls started afterwards, which the change doesn't say.