No, that's a bullshit definition imposed by nuance-allergic 'either you're with us or you're against us' ideologues. Someone who consistently avoids taking an explicit stance on issues is not a centrist. Fence-sitting is not centrism--they're only "so-called centrists" because ignorant people like you label them that.

A centrist is someone whose collective of views/stances is such that it would not really be accurate to label them with "left" or "right". Furthermore, people like you also, in my experience, don't seem to realize that, for example, "left-leaning" and "right-leaning" are in fact subcategories of "centrist"--the "lean" describes the direction that the majority (but not all) of their positions go.

The irony is that a lot more people can be accurately described as "centrist" than actually self-identify (or are accurately identified by others) as such (partially thanks to people like you constantly using the term incorrectly), while the hardline ideologues of both wings arguably hate 'people who agree with them more than they disagree, but won't go as far as they do', more than they do the ones at the opposite end of the political spectrum, and call them "centrists", instead of the ones for whom the definition actually applies!