In MIDI land we must remember that linking the Octave Number CX to a definition is a mistake - in MIDI there is no consistent X - there is a Middle C, it is Note 60, but it’s not anchored to any set CX reference as in MIDI terms it is not transmitted/relevant
Some developers/manufacturers have historically adopted a reference - so for some (as you attest) it became that C3 is 60/‘middle-C’ but that means you have to have negative CX nomenclature for the first two octaves - thus C-2, C-1, C0, C1, C2, C3 … in this regard if you consider the end user using a small LCD with limited display potential having a ‘logical’ standard whereby the first CX is C0
Take a 88 key digital piano, its actual Middle C (~261Hz) in an educational setting by modern standards (the first C note under the treble clef) will be referred to as C4
So for some Middle C is notated C3, C4, C5 - in MIDI it is simply Middle C = Note 60, found on a digital piano, but if you were to extend that back to MIDI note 0 you’d be notating that C-1
So there’s a number of systems based on older notation standards and adapted to digital/logical constraints - it appears that Elektron are 1 octave out compared to the less logical but accepted standard whereby a digital piano has Middle C as C4 as 60, but midi can theoretically permit a note value 0 so we end up with C-1 which is odd (even though in the real world you’d be around 8Hz and it’s all a bit theoretical)
I don’t think there’s right or wrong per se, but due to the lack of understanding of there being many root causes for this situation it leads to a lot of misunderstandings and crops up once a month here
Googling this stuff can add to the confusion as many have a fixed answer that doesn’t reflect the various reasons at the root of this admittedly confusing situation 