TSSOP-28 package is manufactured by many companies, and so many datasheets exist involving this package. I am sure if you will take a dozen of datasheets detailing footprint for this type of package, you will have at least two versions of pad sizes.
In your particular case I think someone, creating devices for these chips, took TSSOP-28 package from ref-packages library and applied to the device without comparing to particular datasheet.
I had a case when I designed footprint for the chip as manufacturer advised, and soldering chip by hand was simply nightmare - because pads were just short for proper access by soldering iron to put solder onto.
Thus if manufacturer recommends longer pads I would follow its advice. Regarding width of pads - up to you, depends on hand soldering skill you have and flux you use.