The car one is the hard one
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The temperature
The interior of a closed car in sun reaches temperatures well above a warehouse or a bathroom. Everything about the product and the package is tested harder there than anywhere else in this property.
PET stops at 120F
Which is a temperature a car interior passes easily. For a product specifically sold to live in a car, the resin chart is a real constraint rather than a background fact.
Which argues for glass
There are 57 glass containers on this shelf. Glass is indifferent to the heat, it reads as premium, and the trade is weight and breakage in a moving vehicle.
UV as well as heat
Sunlight through a windscreen degrades fragrance materials and fades dye. Amber glass or an opaque sleeve protects the contents; clear glass shows them fading.
And the sprayer sits in a hot liquid
Seals, the dip tube and the spring are in contact with a warm alcohol-bearing product for months. Testing the closure at room temperature tells you very little about this use.
Size follows the space
A car product is small, because it lives in a door pocket or a cup holder. The bottom of the 30 to 250 mL window rather than the top.
Say the storage condition on the label
Not in sustained direct sun is a sentence worth printing, and it is one the customer will ignore. Designing for the abuse is better than warning against it.
The customer will leave it in there
Whatever the label says. A car product is designed for the worst case because the worst case is the normal case, and a product that only survives careful storage will not survive this one.
Which makes it a good test of the whole range
If a formula and a package hold up in a car, they hold up anywhere else you will sell. Running the car condition first tells you about all five leaves at once.