Pink Elephants on Parade...
Speaking as an engineer, "enhancements" can mean any improvements - including ones like restructuring/rearchitecting things under the hood to provide a foundation for future development or just to hopefully stop quirky things with the system (EG I worked on a system that was notorious for behaving erratically when a system got under heavy load - It happened very rarely (once every few months but it was steadily increasing in appearances as the company grew) and manifested itself in different ways. From the logs we knew a specific section of code (comprising a sub-system) seemed to be common across all instances and we knew the design of this particular area was bad and might be contributing to the problem but we could never reproduce the scenario nor confirm it was the culprit. So we spent 3 weeks rewriting the subsystem and submitted it as an enhancement but didn't say that it would fix that issue because we didn't want it marketed as such (we just didn't know for sure and didn't want to make a false promise)
The problem has never come back and since then we've pointed to the change as the reason why.