I'll refer you to the article mentioned above.
A very brief look that compares the basic contents of the various Vinayas shows that they differ. The number of precepts, etc. are not the same.
Although earlier studies which focused almost exclusively on the Pali tended to suggest that the Pali Vinaya was perfectly unaltered and it was the others that had been "tampered" with (and other loaded words), there is also very good evidence to suggest that many schools had added a few more precepts to their Vinayas. Mostly fairly minor stuff, actually. The major precepts are largely left unchanged in all the schools.
Alteration does not imply distortion. There is plenty of evidence that most of the early Buddhist material has developed somewhat over a period of time, but this does not necessarily mean that it is distorted, ie. erroneous, false, incorrect, etc.
Often people think that being different, or altered, is always through some sort of nefarious "tampering" and "meddling" and other such ideas which are largely derogatory. However, given the nature of development of oral literature, and even early forms of written literature, this may be be the case. Small changes may occur for other reasons. And these reasons may be fully in the same intent and spirit as the original.
I am not sure which council you are referring to? The first, second, third ... seventh?
My recently moved Blog, containing some of my writings on the Buddha Dhamma, as well as a number of translations from classical Buddhist texts and modern authors, liturgy, etc.: .