This is one of those questions that will generate as many answers as there are people
I think the origin of the "1.3" method is from writing down the tacho/hobbs time. It is very common.
If you own your own plane and look after the maintenance, and use the CAA logbooks, they have columns for "hours" and "minutes" in which case you may prefer to log your flying time as say 1:25 (1hr 25 mins) also.
Obviously the 1st method is easier to add up. The second one is harder unless you have a hh:mm calculator or a spreadsheet whose cells can be formatted to hh:mm...
Otherwise, it is of no consequence.