Only from the point of view of atheism per se, which is why the only definition mentioned in the Wikipedia article you cite that characterises it as such is from an atheist dictionary. Otherwise, it is described alternately as a position, a philosophy and – in the political terms under discussion – a principle (or, as I put it, a value).
Correct, but we’re ralking about the liberal-democratic state’s indifference to the cross, and not the state employee’s indifference to it. Putting aside Quebec’s specific long-standing hypocrisy in its version of secularism, the liberal-democratic state’s embrace of the principle of secularism ideally means that it should be indifferent to a citizen wearing the cross or any other religious symbol – its preferably diverse group of employees included.
According to anyone who’s familiar with the history and philosophical underpinnings and political development of liberal democracy, going back to the 18th century to the present day. Hypocrisies like Quebec’s and France’s don’t define the principle.
That isn’t a problem in a pluralist liberal democracy where the authority figure may adhere to any one of a number of fairy-tale-based personal value systems, or none at all. It is a problem only when, as in Quebec for many decades, the authority figures were in large part drawn from one sect of a larger fantasy-based values system.
But let’s assume that the authority figure is biased on the basis of personal religious beliefs. Prohibiting wearing the religion’s outward trappings doesn’t make that bias vanish – if anything it hides it.
In the end this law is the product of yet another Quebec nationalist party pandering to a bunch of bigoted and xenophobic rural white Catholics who haven’t given a moment’s genuine thought to the relationship between secularism and the liberal-democratic state.
So again: if you want to be seen as a liberal or progressive, act like one. Being an atheist isn’t enough to achieve that by itself.
[And to be clear, I say this all as an atheist myself, one who loathes fundamentalist religions and who approaches all organised religions with a healthy and well-warranted distrust.]