Material
On this page10
The wording
The definition is of "a plastic bottle or container". Material is in the definition rather than in an exception, so a non-plastic container is simply not the thing being banned.
Which puts glass outside it
A 50 mL glass amenity bottle is not a small plastic bottle, whatever its capacity and whatever is in it.
Our shelf has 28 glass containers
13 of them under six ounces. That is a small set and it is a genuine answer for a property that wants individual bottles and has to comply.
Glass in a hotel bathroom is a real objection
Wet floors, bare feet and breakage. Many operators will not consider it for exactly that reason, and that is a sound operational judgment rather than a compliance one.
So it suits specific properties
A spa, a high-end suite, a vacation rental with a bath rather than a shower. Places where the amenity is part of the product and the risk is managed differently.
Aluminium is the other direction
Not plastic, not breakable, and increasingly used for this exact reason. It is not on this shelf, which is worth saying plainly rather than leaving to be discovered.
Do not assume other states match
A statute elsewhere might define the banned article by capacity and single use without reference to material, in which case the glass route closes. This is the lever most likely to differ.
And the spirit of the rule is plastic waste
Which means a glass solution that is thrown away per guest satisfies the text and not the purpose. Worth knowing when a customer asks what their guests will think.
So material is a route, not a recommendation
The text does not reach glass, and that is worth knowing precisely. Whether glass belongs in a wet guest bathroom is a different question, and for most properties the answer to it is no.