Mycorrhizae were all the rage for tomatoes back in the late 90's and early 2000's and at one site where I posted one fellow was selling it.
At that time several folks grew their tomatoes, the same variety, with and without myco and found no difference.
I've wondered myself since myco's are known to increase both water and P transport thru the roots and were first discovered in the SW associated with corn plantings of variouis indigenous Indian groups in terms of growing corn in the absence of much rain, whether it's related to different soils that do have xs P and plenty of rain that makes the difference when some find that mycos help and some find that they don't, when talking about tomatoes.
Lousy paragraph as one sentence I know, but what you see is what you get.