UPC Manual Question

[U376977]

I know a 22 year old preacher in the UPC. He holds their 1st tier liscense (I forget what it is called). He was taking a few appointments regardless if they were UPC churches and he ministers on Wednesdays for his grandfather, who has an independent church.
His UPC pastor, who is also the district super. just had a meeting with him and told him that if he ministers anywhere that the host pastor must contact him (the UPC pastor). The reason he gave was that "you are young and I don't want you to get messed up with a false teaching." And he said it was a manual requirement.

Why does the UPC have this as a requirement? It seems to me that whatever the motivation might be, that the effect would be to completly shut down any ministry outside of the UPC since almost no pastor is going to call a UPC pastor and be questioned about his beliefs when all he wants is to book a guest minister. And what if the host church was trinity, word of faith, etc., cannot an UPC minister to those people if invited?