Google has millions / billions of users. From a security standpoint the focus should be entirely on the root domain, that is the only really meaningful root of trust.
If you are talking about a security issue - the KEY security issue is ANY lack of clarity around root domain.
"Showing the full URL may detract from the parts of the URL that are more important to making a security decision on a webpage." is a statement they have around this change.
I think I agree - I suspect other browsers will have to copy chrome (again) in de-emphasizing the leading URL (often used for fishing).
Folks seem to miss the fact that google chrome was a minor competitor initially it IE - and their focus on things like ... security ... helped them become absolutely dominant. A fair number of enterprises have (finally) started slow slow switch to mandating chrome.