"May delay"!?! Where is the statement that confirms what laws they were following?
However, let's suppose they followed the law's of 18/19:
Handling the ball
Handling the ball involves a deliberate act of a player making contact with the ball with the hand or arm. The following must be considered:
• the movement of the hand towards the ball (not the ball towards the hand)
• the distance between the opponent and the ball (unexpected ball)
• the position of the hand does not necessarily mean that there is an offence.
The goalkeeper has the same restrictions on handling the ball as any other player outside the penalty area. Inside their penalty area, the goalkeeper cannot be guilty of a handling offence incurring a direct free kick or any related sanction but can be guilty of handling offences that incur an indirect free kick.
Under the above laws it's categorically not handball, as all three areas of consideration comply with it not being handball given the actions of Sissoko.
The added complexity that you alluded to in your earlier post was that the interpretation of deliberate being played in Europe but not in PL and where you gave examples of Rose incident was all centred around the act of intent and the interpretation of "deliberate". In Europe the Officials were applying their definition of deliberate if the player was making a deliberate act to block the ball, the handball might have been accidental e.g Rose deliberately made an action to block the ball, in doing so it hit his arm, it was therefore given as handball (the block was deliberate). Same happened in the PSG vs Man U game where a PSG player jumped to block a ball being kicked into the box, the player had his back half turned, eyes closed. It hit his arm and handball was given because the act to block the ball was deliberate, even if the act of handballing it wasn't.
Sissoko made no attempt to block the ball, his arm was already outstretch pointing before the ball was kicked, there was zero attempt made to block.
So, take your pick of the two different laws in place (or not as the case might be), then apply the interpretations of the law, PL or Europe. No matter what way you cut it, no matter what law you choose, it's 100% not handball.
Irrespective of this and back to the wider subject matter of VAR and it's use, had the officials in Madrid spent more than 23 seconds (1 view/angle of a replay) reviewing it, they would have no choice but to not award a pen (under existing or new laws).