Just because something is mandatory, doesn't mean it's enforced. You got 6 million trucks registered in the EU alone [1], plus fleets of trucks registered in adjacent states such as Turkey or Serbia, or old trucks out of the new Eastern European states that predate their EU membership and, with it, mandatory governors. And loggers can be manipulated as well, if you do it right there is no chance of finding that out without taking apart the truck.
Not every country is as thorough as Germany is in technical inspections, trucks from outside the EU don't need speed governors, and as long as you don't race your truck in Germany, France or Austria, chances are high no one will be bothered enough to pull your truck over for a detailed inspection on an examination wheel. Or you simply have two datalogger cards, that you swap out when going into one of these countries.
The enforcement and verification of tachographs grew significantly in last 20 years across whole EU, even in our eastern european countries.
So, again, I very much doubt that there's a mass scale, country-level, tachograph fraud happening in Baltic states without anyone else noticing.
And having been part of EU business that does trucking, police REGULARLY pull over trucks for tachograph inspections (including rest and speeding) even in southern and eastern europe. Any truck business owner would be rather insane to risk the fines tachograph fraud gives at any consistent rate.
Do companies and drivers try to break the law? Yeah, I believe that. Do trucks systemically, constantly drive above speed limit in Baltic states and noone is checking that? BS.