No, that’s not what I said; I said you couldn’t measure to a defined target if the target itself is dynamic.
You can ‘still’ measure to a defined target like NAL2 if you want verification of results, the problem is that due to the conditional programming of the hearing aid, the result in the field is potentially going to differ.
This means that the people using REM as the holy grail for fitting and making a huge song and dance about it online - ‘Don’t trust your Audiologist if they don’t use REM’ etc. aren’t necessarily correct. They might have a method that tells you the arrows are landing nearer the target, but it’s not perfect; especially with more modern dynamic aids.
How many times on here does someone write: ‘my aids sounded great in the booth/soundproof room/shop, but as soon as I went to X they performed differently’ ?
I like REM, I like the fact that it removes some of the subjectivity from ‘does that sound clearer?’, but use it as an absolute measure and you’ll come unstuck - pretty much as they did in the early REM use in the NHS where they mandated it and ended up overprescribing a whole load of hearing aids. OTOH, if you ‘can’ accurately reproduce the complex sound-field of a restaurant with real conversations mixed into the clatter in your fitting centre, then go for it. Preferably with ‘Live Speech Mapping’ to see the output rather than a strict NAL2 line.
Until then - fitting to a basic estimate (with a splash of REM) and developing a client focussed prescription from there, isn’t a bad answer.