The LizApp does show on the second page on what Matt did to her on that night. It shows he kissed her once, groped her twice, and facialized her. So technically he did not go all the way, he just jerked on her face and exposed chest then took a pic/vid.
This is now common on Bull's tactics. If they go straight to sex, they risk it being just a one time thing. So he needs to make sure she is trapped in the blackmail, slowly training and corrupting her, until he goes all the way, until she reach the point where she is the one seeking him for sex. This will explain that he did not initiate sex during that first night but did something enough to be a blackmailing material, making Liz still a virgin and the app confirms its accuracy.