They are popular here - its a compact filter, I prefer them to blown treatment plants, they don't allow blown for holiday homes here because of start up times.
There are shallower options but if the site allows these can be installed in a pack,ie tank and filter come bolted together and one approx 3x3 hole - about 1.12 below invert then your overdig.
One disadvantage is the filter media tank is always empty so in a high water table they recommend strapping down - sheet of steel mesh / bars and 20cm underneath them and round.
We install a few différent types makes of compact filter, some do a single tank solution now, been installing à long time and last few years things have really come on.