ᐅ Are sealing collars necessary for water connections?

A friend of mine is a plumber and occasionally visits our construction site. Today, he told me that the sealing collars are missing from the hot and cold water connections in the shower and bathroom. He said this should not be the case.
When I brought this up, the site manager said that sealing collars are not necessary and that silicone could be used instead.
My friend disagrees and warned me that a silicone seal might leak over time.
Who is right? Are sealing collars required by regulations?

The tradesperson is right! Sealing collars must not be omitted; the risk of water penetrating the wall is too high.
And silicone, dear site manager, is not a durable sealant for bathrooms.
Sealing collars are, so to speak, mandatory, as they are part of the waterproofing system along with corner seals (please refer to the installation instructions provided by the waterproofing system manufacturer).

Your tradesperson friend knows what they’re doing; the site manager apparently does not.