This is how we decide on our ratings and how they work.
An LED rating as excellent will have no or only very minor imperfections in visual performance. It will dim to 1% or less of maximum output and will not have excessive peak currents meaning a decent number of fittings can be used per circuit.
A very good rating is given to an LED that has only minor flaws in its visual performance. These might include a slight shimmer while fading or a slightly uneven profile.
A good LED will have either a single significant flaw (big step in output range, very noticeable flicker when fading) or several more minor flaws in visual performance. Sometimes an LED with visual performance that could be rated as "Very Good" may be downgraded due to a high peaks meaning only a small number of fittings can be used per circuit.
Neutral rated LEDs will have several significant flaws in there visual performance or may perform well above a certain dimmed level but have very noticeable bottom end flicker. It may be necessary to edit profiles for a neutral rated LED to bring it up to an acceptable standard.
This lamp or fittings has sufficient flaws that it would not be acceptable to most users.
This dimmer is unsuitable to test with this LED. For example the manufacturer may have stated that the LED is dimmable by trailing edge only.