I accept that when you show me real world examples of it with a biological explanation.
You wanted a biological reason, if you do want to counter it, give me a better biological reason.
Elves live hundreds of years and dont need to sleep. Some have innate magic.
Dwarves live hundreds of years and have a natural resustance to poisons.
Gnomes have an adult size of roughly a human toddler live hundreds of years and some have innate magic. No mention of interbreeding with humans.
Halflings have an adult size of roughly a human toddler yet can move at the same speed, lift and carry exactly the same amount as a medium sized creature. No mention of interbreeding with humans.
Orcs can instinctively just not die when they should be killed.
Warforged..have no biological mechanisms that I am aware of.
Tieflings have innate magic and explicitly fiendish heritage.
Aasimar have innate magic and explicitly celestial heritage.
Genasi have innate magic and explicitly genie heritage.
Dragonborn..breathe elemental energy.
Aaracockra can fly and have an explicitly shorter lifespan.
Lizardfolk have scales, have a natural swim speed, and hold their breath for 15 minutes at a time.
Tortles have a big-ass shell they lug around.
Tritons have a natural swim speed and can breathe underwater.
Shifters and Changelings can change their entire body structure
...etc.
All of these indicate biologies which differ dramatically from humans. Enough so, that any kind of argument that insists that they must have limitations substantially similar to real-world humans falls flat on its face for me.