More likely a human sub-editor on a paper like the Sydney Morning Herald, surely.

Yes I would think so too

why would a spell checker prefer altitude over attitude?

I would think that even a slightly sophisticated spell checker would catch this. So arguably a lack of automation. Could of course be a human machine interaction problem, where the misguided human and machine makes errors together.

Australian here. SMH is known for a generally poorer standard of English usage and editing compared to other news publications (e.g. The Australian).