'the hours of non-hours work worked by a worker in a pay reference period shall be the total of the number of hours spent by him during the pay reference period in carrying out the duties required of him under his contract to do non-hours work.'
The problem they encountered is that the government still needs to be able to specify what they mean with precision. So what happened is that common words became overloaded with specific and often non-obvious legal meanings.
People at large with no clue how to "speak government" still didn't understand what the government said, but instead of a bunch of known unknowns it turned the language into a minefield of unknown unknowns.
(This got at least some attention notice during the covid pandemic, during which there was clear miscommunication between the government which used 'recommendations' to mean a strong non-legal mandate, and parts of the public which took it to mean helpful tips, like a movie recommendation)
Yes, they are both voluntary, but the nuance is quite different. That ambiguity in nuance is a problem, given that "recommendation" is the strongest wording for a non-legal mandate the Swedish government will use.
Unfortunately that distinction was deliberately obfuscated by the UK Government during the COVID crisis. They would issue "guidelines" that you could be arrested for violating. As I recall, they began as real guidelines, and morphed into legal mandates without ever becoming laws.
Just as programmers invented programming languages to unambiguously express an idea, the legal system uses legal jargon to unambiguously express an idea. Getting rid of jargon means you need to express specific meanings some other way. The Swedish government chose overloading specific meanings to ambiguous words, which is really strictly worse than legal jargon.