You had me going there Eric. I bought what was advertised as elongata seeds and have germinated them. There is allot of contrary information on elongata. What I make of these contradictions is that no, elongata is not a sterile tree. Like all paulownia seed germination is picky and requires a sterile substrate. My guess is that there are hybrids of elongata that are sterile. Check link below for research done on propagating elongata seed in a sterile substrate. I stratified in the fridge for a week or two and then put them in a container of filtered water and bingo. It can take awhile to sprout if of not warm enough. My first batch took forever and I thought it was a fail. My second batch placed out in the summer heat took much less time (maybe a week?)
https://www.researchgate.net/figure/Adaptation-of-Paulownia-plants-on-sterile-substrate-of-P-elongata-x-fortunei_fig5_289255714
