I'm not making a claim. Rather, I'm asking a question. If one could make a summation of, say, the practices of the four major tariqas (Qadiri, Naqshbandi (not sure which one would have been around at his time), Chishti, and Suhrawardiyya) and then ascertain which of these practices are explicitly mentioned in the Sunnah as legislated, then this would certainly be a vast proof in favor of Sufism. However, I am myself aware that this is not necessarily the case in terms of how people argue for Sufism. For example, in Maulana Muhammad Zakariyya Kandhalwi's treatise, Shariat and Tariqat, he instead takes a different tack- I'm sure you've read the book.