There are a lot of various explanations apparently depending on which ISP you talk to.
@NeilO until the last couple of weeks Gfast was available ( not that I can afford it) but it is now amber
Also if I check using the website, as a new customer , what I can order as Ultrafast is only the 152Mbps package whereas previously the 300Mbps was available. I haven't bothered the FTTP team as I'm not buying it.
Just guessing here, I wonder if it is because there isn't sufficient capacity in the backhaul to support the volume of take up of the 330M service. I.e nothing to do with sync speed capability, but rather throughput capability.
I've emailed the G Fast product manager in BT Wholesale to see if I can get an explanation for this result, when I hear back I'll let you all know the outcome.
To clarify the amber result simply means that Openreach are recommending that the G.Fast install is done by an engineer rather than the self install option that is being trialled by them at the moment, it won't prevent you from ordering and doesn't indicate any issues with the line.
I hope that clears things up?