The argument made prior to this is not that an unemployed person is equal to a continuously employed worker but merely that unemployment should not and cannot affect your qualifications for position X. The law is pretty general as it states an employed person is anyone who does not have a job, is able to work, and is seeking work.
If Eric, Yenina, Ursula, and Larry are all able bodies, placing Ursula in her own category based solely on a gap year is in itself discriminatory.
The parent comments are taking the gap year into account—something that can be elaborated on, but should never be a deciding factor. The general consensus ITT is that Eric automatically is a better fit for position X than Ursula based solely on their employment history.
That argument in itself shows biases toward length of employment and current status, with the latter being something that should be irrelevant in a hiring process.
Edit: to show an example, most job postings on P&G have this disclosure:
>Qualified individuals will not be disadvantaged based on being unemployed.
That one line is what everybody is arguing againat, that unemployment automatically declines your qualifications.