As most readers know, Philipp Maas (elaborating on a short article by Johannes Bronkhorst) has claimed that it is highly probable that an independent Yogasūtra never existed and that we should therefore only speak of the Pātañjalayogaśāstra, a work including what is known as Yogasūtra and what is known as Yogabhāṣya. He notices that the Yogasūtra is not independently transmitted, that all quotes until the 11th c. refer to either the YS or the YBh in the same way, as if they were the same work. For more details, see section 2 of his article in Franco 2013 (available here) and his article in Bronkhorst 2010 (available here).
Federico Squarcini recently disputed this claim on the basis of the fact that it is too much dependent on the manuscript transmission, which is not so meaningful, given that all manuscripts are centuries later than the YS–YBh:
La maggior parte di quelli datati fra essi (manoscritti dello YS–YBh) è del XIX secolo. […] non si conoscono manoscritti degli Yogasūtra più antichi del XVI secolo d.C (Squarcini 2015, cxii).
Squarcini also mentions as an evidence in favour of the distinction of the two texts, text-passages such as the following of the YBh:
iti patañjaliḥ etat svarūpam ity uktam (YBh ad YS 3.44)
Here, the author or the YBh seems to quote from the YS as a work by someone different from himself, called Patañjali.
If you read Squarcini, Bronkhorst and Maas, which arguments convince you more?
On Maas 2013 and Maas’ view on the single author of YS and YBh, see here.