I will say it again for the deaf among us... There is nothing to hold the sealant in place, and nothing to clamp it.
As the tube is covered in oil the sealant won't stick, and there isn't another mating surface to hold it in place, hence why it will break off and float about the engine. It's a slightly different application to sealing the sump as there is a 20mm lip holding the silicone in place, plus you would be able to scrape it clean first and brake clean it.