Does anyone know how to get assigned row 20A/C or 20H/K?

This is the first row of Y at the bulkhead. I called GF and was told they could only be requested and under Airport control. They said It could only be released or guaranteed at airport check-in.

Is this true? Or could it be possible to reserve these seats at OLCI?

Why are they blocked? Is it because of bassinet or is it for status passengers?

Thanks for any help.