... and as a follow-up, Gang provided a sage observation here to solve my conundrum about the third set of differences:
There are two subvolumes that can be used here: the "-idat .." and the "-ithr .." ones. This is because with something like a t-test, we often have both an effect estimate and an associated statistic from the modeling here---in general, both should be used in reporting, see here.

Above, for the t-tstat case, the effect estimate subvolume index is 10 and its statistic is 11, so therefore we use "-idat 10" and "-ithr 11"---clusterizing is performed *on* the ithr subvolume, but we keep information around about data in those clusters, and it is actually the idat information that is shown in the "-pref_dat .." output. And, it is actually the idat subvolume information from which the CM RL, CM AP, CM IS, Mean SEM and Max Int, MI RL, MI AP and MI IS information comes from. And indeed, the "peak intensity" of the effect estimate can occur at a different peak location from a statistic. Therefore, one would expect many differences in those columns from just the statistic info.

In the F-stat case, the statistic does not have an accompanying effect estimate, so the '-idat ..' and '-ithr ..' subvolumes are the same thing---just the F-stat. If you changes the t-stat command so that the '-idat ..' and '-ithr ..' both loaded in just the t-stat volume ("-idat 11 -ithr 11"), then the table columns match the F-stat everywhere except for Mean, SEM and Max Int, as expected. NB: I am not recommending doing this for the t-stat in the final results you use, because the data information that accompanies the t-statistic is useful, but just for consistency checking.

I will update this information in the program help file, too, to make these things clearer there.

thanks,
pt

Additionally, the idat info is shown in a couple places in the table, too

For the F-stat case, there is no associated

So, for the t-stat case

In the 3dClusterize command for the t-stat,