It appears that if you open a midi track with a drum map associated with it, Cubase “knows” to open it with the drum notation. Is there a way to override that so the default opens a midi track (regardless of a drum map associated with it) with the key editor?
Preferences/Edi… ahhhhh I’m gonna leave the rest for you to discover.
In general when you are asking a question like “Can I make it do X and not Y?” Preferences is the first place you want to take a glance at. 
Might be obvious to you to look in preferences, but it wasn’t to me.
file>preferences>editors
Default mid editor: set to “Open Key Editor”
uncheck the box “Use drum editor when drum map is assigned”
I didn’t think it was obvious to you. Which is why I pointed out that it something you should put on your ‘check here first’ list for the future.