It's completely different from Laporte vs Spurs. That was an attacking play and the handball law says that a side gaining possession off an arm means it will be ruled out (Elleray of IFAB has confirmed this interpretation to someone on BlueMoon).
Alli's is a defensive one, and a different standard is applied. The 'under pressure' line is very strange though, as this isn't a standard and isn't anywhere under the laws as far as I know, and almost certainly can't be reffed consistently. His arm was above his head for no good reason, and I think it should have been given. The explanation looks like flannel to muddy things more.
The Silva/Bournemouth incident was in the period when they were overturning nothing - the last two weeks seem to be under a different approach.
Which is ludicrous, as you can still gain possession in your own box with a defensive one and score off it, then they bring it back for a penalty, but if you miss it is a goal kick.
Therefore you get punished for scoring.