Seriously contemplating something is semi-synonymous with being on the verge of doing something.

From my perspective, Tuesday would feel like "seriously contemplating" from the inside; even late Monday night could too I think.

So I disagree with the quoted sentence.

EDIT addition for clarity: Had I personally felt like the "Tuesday" scenario described above, I could easily imagine myself describing the event as "seriously contemplating suicide," regardless of what other people think about the definition of "seriously contemplate." So it seems wise to me not to dismiss the possibility that when someone described their situation, it may be less serious than you personally think should be the definition of those words.