Any damage done by a high pH prespray will not be corrected by a neutralising or acidic rinse. Period. A rinse will stop the damage progressing at the point of treatment
You will often not see or be aware of any damage, but it will have occured. Gradual colour loss (fading) and with one, two or even ten cleans down the road, dye bleed may occur as well as more significant fading. Accelerated wear will occur as the fibres will become more brittle and disappear at a faster rate up the customers vac over time.
Having said all that, we the cleaners as well as the customers are unlikely to notice all of this. I would also go as far as recommending that with heavily soiled/trashed wool, subject to testing, use your high pH supersuds with a neutralising acidic rinse. If a safe on wool product wont clean the carpet, it's pointless going through the motions. High pH also tends to be quicker.
I would add that in many commercial installations with wool carpet, they will be changed for aesthetic reasons rather than their performance, and a refit is often before the carpet needs replacement. This environment will typically demand the lowest price and quickest turnaround, so high performance but less than ideal chemicals rule the day.
Safe and happy cleaning
The Ken