If Teflon impeded the reaction but borosilicate did not help it, then the two Teflon flasks would have had identical results. They didn’t have identical results

If Teflon impeded the reaction but borosilicate did not help it, then the two Teflon flasks would have had identical results. They didn’t have identical results, therefore logically one can conclude that borosilicate has a beneficial effect. Yes, it would take more experiments to further explore the role of the vessel material. This is how science works in general; someone gets an idea and runs a limited experiment and gets results. Then other people, seeing the results and understanding the limitations, get their own ideas and test those. What I’m trying to say is that you’re not wrong to say there is more to test here. But, it’s not a fatal flaw to this experiment. All experiments have limits to what they can prove.