Not withstanding that Opera, Firefox, and other browsers are available in the Google Play store for android, you can easily change the default search in the Settings menu. The ease of this change can be compared to changing the default search in Internet Explorer or Safari. [1]
Its not irrelevant; there is clearly a stronger case for anticompetitive behavior if you include an app as default with an OS and prevent alternatives than you if you provide a default but allow alternatives.
OTOH, merely allowing alternatives may not be sufficient, depending on other circumstances, to not run afoul of competition laws in some jurisdictions.
But the landscape has changed quite a bit since the days of Microsoft bunding IE. Changing browsers and search engines is a trivial task nowadays.
Plus, Microsoft's problems were tied to Windows with IE. It appears this is just about Search results and/or Chrome, as they outline Android specifically as something they are now investigating.
It's less irrelevant when the OP used the particular phasing of "mandates", which is quite hyperbolic and doesn't actually forward the discussion, thus the corrections.
[1] http://www.androidcentral.com/how-change-your-default-search...