A guideline can also be considered an accepted engineering standard, so your statement is not correct.
Unfortunately, the LAI guideline is not an accepted engineering standard. It must first prove itself in application. How long that takes... courts have decided that about 3 years after introduction, a guideline can become an accepted engineering standard if it proves itself.
At the moment, 4 out of 10 builders follow the authorities’ recommendations, and with the others, there is stress.
The fact at the moment is: authorities can issue a recommendation in statements according to the guideline (location, xx meters distance, device), but if the builder does not comply, the authority has no power if immission limit values according to TA Lärm are met. In monitoring (device bought and installed via Amaz..), the distances according to the sound power level of the LAI guideline do not matter, since they are not legally binding; here assessment by the lower immission control authorities (districts) is exclusively according to TA Lärm (think of the urban area, 63dB during the day, 48dB at night... well, cheers!).
Actually, these devices belong in the 32nd BImSchV. An amendment to this was planned from 2013 and was sunk for political reasons by the federal government at the end of 2015 (in my opinion, the motives are the Energy Saving Ordinance, the Energy Saving Act, and the Climate Protection Plan 2050).
The guideline is a source of knowledge for urban land-use planning and only legally binding when established in the development plan (not as a note and not as a statement).
cheers