It would ... however you can see there's actually a mistake in the document. The first example "EA/F1ZZZ" is an example of EA + own callsign, NOT EA + district + own callsign. The second example is EA + district + own callsign as stated, so it does look like the first one is INTENDED to be EA + own callsign.
Whichever way you read it, EA8/ is absolutely fine. And if this is a mistake in the URE document as it appears, then that also confirms with the CEPT document that EA/ would be OK from EA8 too - although you would surely want to be DXCC-unambiguous!
Note that the CEPT document merely requires the EA - but does not prohibit the addition of a region number. "EA8/" would appear to keep everything and everyone happy.