While I deeply respect your belief, I don't think the issue is quite as straightforward from an evidentiary perspective.
Not only are the supposed Janamsakhis of spurious authorship (the earliest materialises over 200 years after Guru Nānak Sahib's birth) but the performance of "miracles" or "karamāt" appears to be antithetical to the hardworking, practical, humanist, down-to-Earth, anti-superstition ethos espoused by the Guru Granth Sahib.
For example, in Sidh Goshat, Guru Nānak was challenged by the Sidhs to display miracles, and he refused, replying that realising God is the true miracle.
I am not saying that these miracles definitely did not happen.
I am simply asking how we can be so sure that they definitely did happen?
In addition, I am curious as to why the Gurus performing miracles is so important to so many people?
How does it affect their belief in Sikhi to say these miracles may not have happened?
If you mean "anti-Brahmin", then I'm not sure Dr. Dhillon necessarily fits this description. He is quite respectful of other peoples' beliefs and accepts that the Vedic and Yogic (as well as Koranic) traditions have their own particular paradigms.
He simply seems to be making the point that Sikhi established its own particular paradigm that deviated dramatically from pre-existing ones, but also acknowledges key overlaps.
If you are saying that Dr. Dhillon is "anti-Brahmān", then I think that's a deeply mistaken belief, since Brahmān is actually the Hindu name for the Supreme Reality (the One God) and is very much at the core of the Advaita Vedanta school of Hinduism.
And finally, if you are saying that Dr. Dhillon is "anti-Brahminism", then I would posit that Sikhi, too, is quite clearly anti-caste / anti-Brahminist in its tachings.
Returning to my original query, however, I am curious to know whether or not you consider Sikhi to be an affirmation of Vedic/Yogic concepts like mantra and reincarnation?