|There's more than one way to do things|
Another justifiction: $INPLACE_EDIT is "clearer" that $^I.
If you don't understand the process set in motion by setting an appropriate value into this magic variable, via either alias; and what constitutes an 'appropriate value'; and what other pieces of magical context are required to make it all work; then you are going to have to look it up. And it is just as easy to look up $^I as it is to lookup $INPLACE_EDIT.
And if you are familiar with the requirements and effect of setting a value into that magic variable, then $INPLACE_EDIT is no clearer than $^I.
The former is in no way enough to explain what's going on, if you are unfamiliar with the operation.
Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.