Well yeah “Dishwasher safe” is an endorsement. The lack of an endorsement is not an endorsement to the contrary. Something is only “dishwasher unsafe” if it says “Hand wash only”

I’ve seen a lot of fabrics that say “Dry Clean Only” because the manufacturer was too lazy, but my experience with dishes finds that the labels are generally quite accurate. Putting a non-dishwasher-safe item in usually ruins it.

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A couple of things come to mind here:

I own a metal one which I assume was dishwasher safe but somehow water got trapped inside the ‘extra’ parts of it which could be unsanitary due to the water eventually stagnating.

Another is that the heat from the dishwasher can warp and silicone or plastic parts which will render them unusable eventually.

Not saying you’re wrong but this is what I consider from the warning they provide.

Usually things marked not for dishwashers can’t hold up to the abrasive nature of the detergent or the heat of the water over a prolonged wash cycle.

Dishwashers are not magical devices, they basically just spray sandy soap-water for a long time.

How would they know what sort o bacteria you cultivate in your abode?

Eh, if the bottle is just for water there’s enough spray and heat to kill and rinse it usually.