This is how we decide on our ratings and how they work.
An LED rated 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 shimmer while fading etc.) 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 peak currents meaning only a small number of fittings can be used per circuit.
"Neutral" rated LEDs will have several significant flaws in their 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 fitting 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.
This fitting/driver has not been tested with this dimmer.