Joshi and Roodbergen left their Mahabhashya project unfinished after 12 volumes (11/85 āhnikas) with this comment:
When we started the Mahabhaṣya-project, our idea was that it could be only through Patanjali that we would be able to understand Panini better. How- ever, we have now come to the conclusion that, apart from introducing a great deal of extraneous material in the interpretation of the Paninisutras, Patanjali is often at a loss to construe Panini’s intention. Therefore Patanjali can only act as a guide to be critically followed, not as the final authority with respect to Panini. The Mahabhaṣya can never replace one’s independent judgment regarding the interpretation of Panini, especially in the matter of anuvṛtti and nivṛtti of rules, and of conflict-solving procedures. We have also come to the conclusion that, to some extent, the Käsikävṛtti has preserved an authentic grammgtical tradition, independent of and different from Patanjali.
विस्तारः (द्रष्टुं नोद्यम्)
SD Joshi would only be allowed into Pune’s pandita sabhas upon the promise that he would not challenge the three sages of grammar in any debate.