If the SCD diet is right, many people might not have obvious issues with bifidus in supplements. It's just that there tends to be enough bifidus in the gut already, but not enough lactobacillus, so the diet simply says it is best to try to increase the population of bacterium like acidophilus, rather than bifidus. All of these bacteria, even the friendly bacteria, compete with one another for survival. Here's a quote from an SCD-post (I included a link - aside from the quote, there's an interesting discussion about
probiotics in the link):
"L. Acidophilus is about as community-minded a bacterial strain as you will find, with S.Thermophilus and L.Bulgaricus running a close second. The others are either less friendly, or are unknown quantities. It gets even more complicated if you consider soil based strains. So we stick with Acidophilus in our supplements, and Acidophilus, Thermophilus and Bulgaricus in our yoghurt, because they are good neighbours."
My daughter uses a SCD-legal acidophilus probiotic she keeps in the fridge. Even though she is going off the SCD diet, she will keep some elements of it intact: staying away from most processed stuff, additives, etc. It is easy enough to order an SCD legal probiotic, so she is not taking any chances and will stick with it.
I'm not trying to sell anybody on SCD - just wanted to explain some of the theory behind it. If you take any kind of probiotic and it helps, great!