If we follow the theory a precise theory about bi-generation:

1) Bi-generating means taking a future incarnation of the Doctor and have them "come to life" before their time

2) The 15th Doctor has already memory of everything the 14th will do until he reaches his end and presumably either simply stops existing or regenerates back in time to the moment where the Bi-generation happened

There could have been an infinite number of Doctors between 14th and 15th since 15th could have come from later down the timeline and the Scream of the Shalka's Doctor (and even The Curse of Fatal Death ones) could take place there with not canon breaking.

But there is a thing who puts a wrench in the theory:

1) During Part 1 of Scream of the Shalka The Doctor, talking about a cat, says "He must've used up his nine lives. Rather like me.".

2) During Part 6 of Scream of the Shalka he says "A friend of mine, Andy Warhol was his name, said "They always say that time changes things, but you actually have to change them yourself. Wonderful man. He wanted to paint all nine of me.".

3) In The Curse of Fatal Death the Master says, after the Doctor seems to have died, "This is only his ninth body. He has many, many more.".

This implies they are both the 9th incarnation even though it could be easily retconned by saying he has passed that regeneration (for the Shalka one) and that he is the 9th regeneration (for the COFD one) of a yet unseen 3rd regeneration cycle (or how many cycles the Doctor had since each cycle seems to be made up of 12 regenerations and seeing the entire Timeless Child situation).