I do not see these as valid reasons.
1.) Your job as the QB Coach is not to design and call plays, so his idea of how to run an offense could be vastly different than that of PC but Curry job is to support and disseminate information to the QB about the best way to execute the offense in terms of what he is seeing out on the field (in the QB room and on the sideline), the Lions of now up for a head coaching gig was the QB coach before Campbell fired the OC and promoted him and he brought his ideas and adjustments to the offense (in season) and their offense has been clicking and top 5 the last two seasons.
2.) Curry (IMHO) was not "tasked" with being the OC at the Senior Bowl it was just and exercise for position coaches to take on a bigger role and what better time to do it than in the offseason teaching and college athletes who are auditioning to become professional athletes, not exactly a ringing endorsement of his capabilities as an OC just an opportunity to hold the call sheet.
Curry should be receiving OC interviews like the rest of these TE, QB coaches and Passing Game Coordinators around the league but he is not, he may not be ready but the Saints think a lot of him as a member of the staff, but not enough to run their offense.