This is really old news.
Adding good bacteria does not change the gut flora. Adding bad bacteria doesn’t change the gut flora either. This has been known for a long time. Only sellers of probiotics claim otherwise (commercial considerations), as do some alternative websites (they adhere to their belief system more than to reality).
There are only two cases where intake of bacteria does have a, possibly profound, effect on the gut flora.
The first is during birth. The newborn baby’s gut flora is kind of “initialized” by the mother’s gut flora. This happens because birth is quite a “messy” process. Of course, this only happens during a natural birth process under natural (that is, not sterile) circumstances.
The second is after having killed lots of gut bacteria. This usually happens after having taken antibiotics. Directly after stopping the use of antibiotics, bacteria may be added to the gut flora.
In all other cases, the gut flora is extremely resistant to modification in any way.