Sentinelese are worth killing per the Dark Forest logic: they are aggressive and have incentive to kill you, so you must kill them before they even get a chance to kill you. Notice how this logic doesn't differentiate between humans and aliens: self preservation overrides whatever compassion you might have.

>But none of those connections would exist between aliens and humans.

That's exactly why humans are more worth killing than aliens: we have conflict of interests with humans but not with aliens.

>We're not one of them, nor do we share the same biome, so our deaths might well be entirely void of meaning or consequence for them.

If the Sentinelese disappear, the biome will likely become only more rich.