That assertion is highly dependent on too many factors and even recent developments to be of much use.

That general assertion needs to be backed up with everything around the soil type, the copper diameter, labour costs, protocols and type of fibre, etc., etc.

And if you’re going down the route of having VDSL ISAMs in the field anyway then you’re certainly going to have the infrastructure there already anyway to support GPON over whatever fibre is in the ground anyway.

And are you sure that by “copper’s capabilities” you’re not actually referring to progressively closer deployment of infrastructure to the customer to overcome copper’s limitations? Because the move from dial any number to the local exchange to a node (FTTN) to now the curb (FTTC) certainly seems to reflect that more adequately.