Thor stats are wrong for disk read/write

It looks like the stats are being aggregated incorrectly (adding the total time each time they are merged instead of the increment).

Some examples:

• The disk write times (5hrs) for a13 are much larger than the timings for the localExecute (20mins). That shouldn't ever be the case.
• Ac28 - a filtered project does not have any timings or other stats associated with it.
• The splitters do not have any timings associated with them
• There aren't any counts on the edges 31->32 and 29->32
• TimeAvgDiskReadIO is wrong for the disk reads e.g., a30. Are they being accumulated too often?
• The disk read sizes for ac30 do not match the write sizes for a20. Nor do the skews

See vault W20210510-092409