You're right about that, just look at their ad-hoc language tests for language school Non-ED visa holders they did in the past.
The current government clearly is very lax about immigration right now, and I'd expect that to be reflected in the level of scrutiny exercised by IOs as well - for the time being.
However, if and when that lax attitude changes again, DTV visa holders could get hassled in the same way as METV and Non-ED visa holders before. If I had to guess based on past performance, the most likely trigger will be a few high-profile cases of DTV holders committing crimes.