It would also be truly bizarre to delete January 5 and 6 but not the 4th, to follow some data retention rule. (Mind you, it’s not clear that that happened, but that seems to be the implication.) Swiss cheese retention is not a standard that anyone would ever have. You might keep data from certain important dates, but not delete certain dates.
The interesting question, I guess, will be whether the Secret Service were competent enough to delete completely, or if these are the usual “specially Trump chosen”?