That’s incorrect if I understood previous comments regarding ghost files correctly.
The DTTG2 data store remains intact as long as either DTTG2 or DTTG3 are installed. I.e. if you remove DTTG2 while DTTG3 is installed the DTTG2 data store is available for DTTG3. Only if you delete both, than iOS cleans up.
Please keep in mind this is what I understood from the comments here, as I obviously do not have the details the developer has.
Edit - Source: DTTG 3 is corrupting files - #134 by eboehnisch