Unfortunately, yes it does. If it has been treated with any kind of pesticide, there is a high possibility the rhizome will go into dormancy, making it somewhat more difficult to detect the scale of the Japanese Knotweed infestation & to give the infestation the appropriate amount of treatment in subsequent visits.
If there have been attempts at digging or removing the Japanese Knotweed, it will be very difficult to recognize the original extent and spread of the plant. Inevitably by trying to remove the Knotweed using the extraction method, it could be spread over a wider area and end up being more difficult and more costly.
The best advice we can give is always try to take advice and service from a recognised professional and accredited firm.