I agree, to an extent, that nutrition and recovery (or excessive training) are likely the major agents of recovery limitation for most.
Just as a note, there are people who have slower recovery for many reasons.
If two people eat and rest optimally with ideal training, one may simply recover damage more slowly than the other.
We train our bodies to recover faster. There are neurotransmitters, hormones, precursors, etc that each of us synthesize at different rates.
That's already close to as intense as I do NOW. And you didn't specify if one would stop at 3 sets per bodypart, or continue up to 4 evenutally?
True, duration is a consideration! Note: Doing the same workout in LESS time is an increase in intensity.
Consider these as you progress: supersets, shorter rests, giant sets, etc...
Two sets, utilized for a period where you milk them for all they are worth by progressing through every imaginable intensity variation over time. Then, A progression to 3 sets is fine. The hormonal response at 3 sets is very good. You likely recover from it fully and so no need to compare your prior training to this. This is a progression. That is what counts.