No, changing pitch incrementally like that will not make larger transpositions sound better, because you're not actually changing it gradually -- every time you choose a transposition value it's recalculating it from the original pitch. AFAICT the best way to get better transposition quality in GB is to use just the Vocal Transformer to transpose, instead of any other method of transposition.
If you transpose all tracks including the vocal with the Key menu at the top, you'll usually get poor sound quality on the vocal -- you could try to improve that by opening a Vocal Transformer plug-in on the vocal track, leaving its Pitch slider at 0 [since the vocal has already been transposed by the Key change], and setting to Formant slider to compensate. So, for example, if a Key change from C to G makes the voice go DOWN in pitch, then you'd set the Formant slider in the Vocal Transformer UP by an equal number of steps. C to G is 7 semitones if the pitch goes up, and 5 semitones if the pitch goes down -- when I tried that Key change it made the voice go DOWN to a lower G [5 semitones lower], so setting the Vocal Transformer Formant slider UP to +5 compensated, for a better sounding vocal transposition, similar to what I got if I just used the Vocal Transformer and not the Key change menu. This seems to work, but you have to know the number of semitones that a Key change is moving the pitch up or down to be able to effectively compensate with the Vocal Transformer's Formant slider, so it requires an understanding of the relevant music theory -- the number of semitones between one key and another, going either up or down in pitch.
Alternatively, you could transpose all Software Instrument track Regions with the Transpose slider in the Editor pane, but transpose Audio (vocal) tracks only with the Vocal Transformer. Then you could just set the Transposition values in both places numerically to the same number, which might be easier -- a little more work if you have a lot of tracks, but it doesn't require as much music theory knowledge about keys and semitones..