Another option to reduce return loss is to insert an attenuating pad before the feed-through terminator.
The two 100ohm leaded resistors used in the Aliexpress through terminator are only 1/8W.
Using smd resistors to improve the frequency response wouldn't make the slightest difference on my 60Mhz scope, and my Spec-An already has a 50ohm input. If done the right way, it would increase the power rating. As the links above in other posts show, it would be cheap and easy to replace the leaded resistors with SMD resistors. If care is taken with the physical layout, then the frequency response should be improved.
Dazz