Earlier quoted context omitted.
A normal local spellcheck requires you to be much closer to the word than an "enhanced" one. As an example, if I search Google for "nucrusift" ("microsoft", but typed with my right hand one space to the left, a fairly common category of typo IME), it suggests a search for "Microsoft". The built-in spellcheck in Chrome (which I'm using to type this comment) does not offer any suggestions to correct "nucrusift".
iOS's local spell check suggested Microsoft.
When I entered that same string into iOS Safari in a text box replying to your comment, deliberately bypassing the keyboard's auto-complete, it had no suggestions.