Be careful with that statement. Most common sequestering agents buffer in the pH range and DTPA is no exception (see page 6). Choosing a different sequestering agent can give you a different pH and buffer strength! Also note that the patent lists DTPA, while the MSDS lists DTPA pentasodium salt, the first one is a strong acid while the latter one is caustic (and much easier to dissolve). If pH is suitably chosen there is a good chance that no restrainer is needed.
Yes, you right. If we omit DTPA or change it to other agent we need correct (decrease) amount of borax for required pH=8.5. This isn't a provlem