Overlapping shape file and coverage

Why can SHP and COV be directly superimposed?

After discussing the problem with netizens today, I did it myself. How can files in two different formats be seamlessly stacked?
Does ArcGIS convert SHP to cov internally during processing, and then overlay it, and then convert it back to SHP? Moreover, if the file name is too long for me to manually convert SHP to cov, it will not be possible to say that this problem will not occur with ESRI's strength? Strange!
The SHP file only saves simple space data, but does not save the topological relationship. Some problems may occur during the conversion of cov, which does not seem to be well solved by ESRI...

I don't know if I have any friends who have done similar jobs. Please give me some suggestions. Thank you!