Totally agree with Ben.
East's has an obligation to make a strong move if East thought 2
♦ is natural.
West's alert of 2
♦ 'triggers' East that the 2
♠ call may be a forced preference. East sees a port in the storm and passes 2
♠ (good thing pard didn't bid 3
♣!).
For those that have problems conceptualizing this issue, imagine if you were playing with screens and you can't hear partner's alert (

not unlike on-line). Would you timidly pass 2
♠? Heck, I'd be making a SLAM try. I don't care about the idea that pard passed over 1
♦. Many of us don't automatically overcall on 5 ratty spades and 10 points. A hand like: Jxxxx, xxxx, Kx, Ax gives us a play for 7.
If I was the director (or on a committee), I wouldn't accept less than the doubled penalty of 4
♠ as the proper adjustment for E/W. Absolutely clear case of UI.
It gets a little murky if E/W can demonstrate that 2
♦ IS conventional and somehow the alert doesn't trigger East (although I can't see how). Interestingly if E/W was playing with screens, and East passed 2
♠, I think East could be given the benefit of the doubt.
Is the existence of West's 2
♠ bid ALONE (i.e. without the benefit of the alert) enough to remind East that they have an agreement here? Curious question.
1♦-( P)-1♥-(2♦)
Pas-(2♠)-ALL PASS
Partner leads ♦J (look at the T98 in dummy), ace wins....