Why would you "nest" keys in the first place? Keys aren't Russian Matryoska dolls.
Just do Ctrl + Alt...
I fail to see what the "bug" is about -- there are no "actual keys or other single units of input" that can't be expressed as <kbd>text here</kbd> + <kbd>text here</kbd>.
The nested keys is a funny concept that serves no practical purpose, but what would you have it do instead? Automatically add a plus sign that you could just type yourself? Remove the feature so it can't be used because it isn't normally used?
Also, just because I can, have a free tower as a token of my gratitude for posting this enlightening question:
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