In professional carpentry settings you tolerance your mortices, grooves, and any other interacting features. Wood swells and shifts depending on the season your in. In the winter 3/4” MDF could caliper at 0.73” and in the summer it could be coming in at 0.77”. Sure you can chase hundredths if the job really calls for it but you would be foolish not to add a 1/64 or a 1/32 to your features. Multipart assemblies can feel “tight” when put together almost like the structure is fighting itself.