What would the path be had you been able to contain the light?

[Lurina]

Which confirms that we definitely wouldn't have ever contained it anyway, because he was testing for something that even we fairly quickly knew was false, our potential Unsundered-ness.

If Emet had ever met Ardbert we wouldn't have had this problem. ...we'd have had an entirely different, probably much worse one.

It's worth nothing that there's a slight terminology issue here. The Japanese text doesn't really have a direct equivalent to the terms "Sundered" and "Unsundered" that are used a lot in the English text. The term that Yoshi-P employs for Unsundered here (and which is also used by Emet in the story) is "真の人/Shin no hito" which literally means "true person", while there isn't really a general term for the Sundered at all. The Sundered Ascians specifically are called the 転生組/Tenseigumi or "Reincarnated Group", while other Sundered are either just referred to as humans or (usually by Emet) 失敗者/Shippaisha, meaning "failure".

In other words, Yoshi-P wasn't per-se saying that Emet was expecting or hoping the WoL to literally be or become Unsundered in a technical sense, just that they would prove somehow that they are equally 'real' people.