There is no such thing as a "standard" premium economy seat pitch just as the economy and business seat pitches vary between airlines and Etihad are not pitching it as premium economy on the basis that I presume all you get is extra leg room
Mind you the picture on the web pages suggests far more room than the reality dare I say more than many business classes
https://www.etihad.com/en-gb/plan-an...extra-legroom/
For short haul economy yes I was happy with Thai Smile nothing special but did the job and far preferable to Air Asia