Welcome! Glad you're joining us from France.
Something like that card -- a simple indication whether there is UVB or isn't UVB -- would be kind of like a thermometer that indicates whether the heat tape is running or not without actually indicating the temperature. I'm not sure what the use would be, and I can imagine numerous common situations in which it would give a false sense of knowledge.
Unfortunately, the 'yes/no' indicator card seems to be something that would further encourage the common 'toss some UVB on there, it'll be fine' practice, which I don't think is good husbandry at all (contra all the keepers who think they're at the cutting edge of care by doing just this).
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