Is it a case here that "we" just didn't hear about it, or that the impact of the knowledge never made it outside the community/region. Did it matter to the people living it? Seems like absolutely yes. Did it endure beyond that community or region? Maybe they do not mean "insignificant" altogether and simply mean insignificant within the context of the ideas and knowledge that endured and were built upon to arrive where we are?
I'm genuinely curious as I feel like this touches on something broader. I think about this with literature and poetry. There's a wonderful effect as you read through time where there are various dialogues happening. People sort of reacting to each other and speaking across generations and cultures. Ginsberg reads differently when you understand his relationship with the Greek epics and other poets before him. I guess my point is, and I may have bungled it spectacularly and just get told I'm an ass, something might not be insignificant unless evaluated as part of a larger context and historic dialog.
edit: removed my ignorant line about the book of optics.