I believe you misunderstand how LORETA (and sLORETA an eLORETA) work.

With such analyses, you can generate "voxels" (much larger than the voxels generated using fMRI) from the raw EEG data that can then be analyzed further and compared with their neighbors in the 3D space of such voxels, so yes, we CAN look at "the entirety of the brain," both in a reasonably precise way time-wise with LORETA-type analysis, and in a reasonably precise way space-wise with fMRI. There is a tradeoff between spacial accuracy and temporal accuracy, depending on which instruments you use to measure. You can't get both with any existing technology.

Now, as I said, TM is a resting practice. ALL benefits from TM appear to come from enhancing the activity of the DMN and eventually that becomes the new normal mode of DMN activity outside of TM practie.

Focused attention and mindfulness are NOT resting practices. Whatever benefits found in beginning meditators due to any restful effects tend to fade over time, as shown in the only longitudinal study on mindfulness that I am aware of (happy to learn of another multi-year study, if you have a reference).

Other benefits, including some not found from TM, persist in those types of practices.

Where TM most notably shines is in the treatment of PTSD. Since it turns out that children in poverty are often suffering from PTSD, when such children are taught TM, their academic performance suddenly improves dramatically.

These are important considerations when a school or government is trying to decide what single mental program they might easily incorporate into a school day.