Invisible is not intangible. Their earlier run in with Locus before their actualization was proof enough of that. The wires go tight in a snare around Sombra's ankle at the exact moment Delta regains control of York's body (such as it is) and realizes precisely how he misjudged the situation. Assimilating a threat to make them less of one- Sombra's hacking skills are second to few in the Legion and neutralizing that is a priority.

Cortana is something he hadn't had to calculate. Something he didn't expect to face- a battle he would not have chosen under any circumstances.

Outwardly the wires writhe and creep, trying to find the ports Delta knows to exist on Sombra's back somewhere. Inwardly? The digital space is a fractal Palace, Delta looking much as he always does, standing at calm attention while awaiting Cortana's intrusion. This isn't a fight he has a hope of winning, and thus? He does not intend to fight.

To converse, however... of anyone, she might be able to understand his reasoning.

Cortana.