The term "rectified" is used but rarely. As applied to essential oils etc. it has no precise meaning and each usage can mean different things. In general "rectified" means that an additional processing step has been performed to remove some unwanted component. I would have to search to find an actual use of this term with essential oils, I believe that I may have seen it applied to bergamot oil that had been treated to remove bergaptene though the more usual designation for this seems to be "Bergamot Oil, FCF". I am guessing that you might also see it applied to essential oils that had been processed to remove terpenes though again the more usual terminology is to say "terpene free".
Your interpretation, stated above, is unknown to me.My understanding, and I may have this wrong, is the non rectified oils use the highest quality and grade of plant leaves in the steam distillation process.
The rectified oils use lower "common" quality plant leaves and parts in the distillation process. After distillation, the end product is "rectified" or put through a purification process to remove unwanted components. It's cheaper because it is less labor intensive.
Do I have that right?
Do you have any links to websites where you are seeing these "rectified" oils?
My usual sources for essential oils or absolutes are Eden Botanical, White Lotus Aromatics, Liberty Natural, John D. Walsh ...
Here is the "rectified" products page from a large British supplier of essential oils:
You can see the many various different terms used. For examples, there is:
"Bay Oil Rectified" and "Bay Oil Terpeneless". I would guess that they both have been treated by fractional distillation to remove terpenes but that the "Bay Oil Rectifed" has a significantly greater amount of residual terpenes than the "Bay Oil Terpeneless".
For certain citrus oils an additional term is "Fold", a Folded oil has been treated to remove terpenes with the degree of Fold indicating the degree of concentration of desirable (non terpene) materials. For example there is Lemon Oil 2, 4, 5 and 8 Fold also Lemon Oil Terpeneless and Lemon Oil Sesquiterpeneless.
This company also has a Bergamot Oil Terpeneless but it is not stated that this is also Furocoumarin Free (FCF) so this oil may still be photosensitizing. Similarly it is possible to produce Bergamot Oil FCF by saponification which would not reduce the terpene content.
Here is a Google book search that has an entry about rectified peppermint oil: