You're right. But, it's less about the storage, and more about the processing. The machines used to process food all have plastic parts, bearing surfaces that wear down.

Studies published in Food Chemistry found microplastics in every commercial olive oil they tested — so olive oil does have microplastics, and the plastic comes from the extraction and bottling chain, not the olives. A 2024 study of olive and vegetable oils from Italy and Spain measured a mean of about 1,140 particles per liter, mostly fragments under 100 microns and dominated by polyethylene and polypropylene — and found no significant difference between oils bottled in glass and in plastic.