The Ondontoglossum in its family tree is causing the thin spikes. They are usually classed with Brassia as spider orchids.
When hybridized with Oncidium they produce larger and more colorful flowers that just the Oncidium.
I have had Brassia with spikes almost 5 feet long and they were as thin as yours. This Brassia from last year is an example. It is the large spider on the left.
I bought the plant after the spikes were already 4 feet long, and it took 10 weeks for the flowers to open. Final size was 53 and 45 inches for the two spikes. For reference to judge the thickness of the stem, each flower is eight inches high.
