The pour and the rinse
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The pour requirement
A nonrefillable container of five gallons or less holding a liquid pesticide must allow the contents to pour in a continuous, coherent stream, and must minimise dripping.
Why that is a regulation and not advice
A product that glugs splashes, and a product that drips leaves concentrate on the outside of the bottle and on the hands of whoever picks it up next. The pour is an exposure route.
The rinse requirement
A rigid container of five gallons or less holding a dilutable product must achieve at least 99.99 percent removal of each active ingredient under the prescribed test procedure.
Which is a specification on the inside of the bottle
Smooth interior, no sharp internal shoulder, no handle cavity that traps liquid, and a neck wide enough to rinse through. Those are mould decisions, made by the container manufacturer long before you see the bottle.
So the question to ask a supplier is specific
Not "is this suitable for agricultural chemicals" but whether the container meets the 165.25 standards for a nonrefillable container, and whether the removal test has been performed.
Triple rinse is the other half of it
The standard exists so that a user following the triple rinse directions actually removes the product, which is what makes an empty container disposable rather than hazardous waste. The container and the directions are one system.
And the DOT standard sits underneath
A non-hazardous pesticide container complies with the DOT provisions applicable to a Packing Group III material. A hazardous one is in the full hazardous materials regime.
None of this applies to a fertilizer
Which is the practical consequence of the classification question. The same jug can be an ordinary container or a regulated one depending on what goes in it.