Gustave:
I have never heard a SDA suggest that the reason for Mary not to touch him was because He might not be worthy of worship, or that He was uncertain as to whether or not His sacrifice had been accepted by the Father.
I will not suggest that there is a clear Biblical picture as to why Christ may have wanted to return to the Father at that time. All is probably speculative and your opinion is as likely to be correct is my opinion on that issue.
In any case, in my thinking the 1st Advent was completed in those few days prior to the report in Acts 1, as Christ guided in the beginning of the organization and functioning of the Christian church.
From this perspective, I see a 1sst advent that has occurred in the past, and a 2nd Advent that will occur in the future.