Vloerverwarming but no connection

Hello, I recently had a company install fermacell vloerverwarming on a studio apartment.

When they arrived they told me I would need to hire a plumber to do the water connection. I asked if they couldn't use the radiator pipes as they were placing the connection in the same spot, and they said those pipes were too small.

I expected that the water connection was part of installing the vloerverwarming, and not done by separate people. The more people I add the more problems.

Is this normal?