The Bengals have one of the best offenses in the league thanks to Joe Burrow and Ja'Marr Chase doing crazy things on the field. In Burrow's first full season after his injury in his rookie season, the Bengals made the Super Bowl, and other than this past season when Burrow was injured yet again, they have been competitive every season.
A solid tight end would help round out the Bengals' offense and make it that much better. They could probably get Brock Bowers with their first-round pick, but since the tight end position is not a giant need, they can probably wait till the second round to pick up Sinnott.
With how much opposing defenses focus on the wide receivers in the Bengals' offense, Sinnott could be a great pickup as he may not seem to be as much of a threat as other offensive players. Again, Sinnott has good pass-catching abilities and could grow a lot with the Bengals.