You may notice a slight increase in cancellation requests, but should receive fewer direct messages from buyers inquiring about cancellations. 

Why don't ebay actually start displaying the listings that buyers is looking at instead of messing around with adding a button to make it easier to cancel once they have bought?

eBay claim to be the home of preloved or recommence market where items are not perfect and faults need to be mentioned. Yet the important information is hidden away to make room for promoted listings.

This is more likely to make a difference and keep both buyers and sellers happy and save everyone time and money. Plus more like to help sellers avoid false not as described defects.