Nope.
“this amounts to 25% of the UK’s nuclear deterrent”
He meant that the 16 missiles - which happen to be Tridents in this story - are 25% of the UK’s TOTAL deterrent of the nuclear type, not Trident type specifically. When he mentioned land-based he again wrote nothing about any of them being Trident.
You’re going back to the OP and missing the point.
In any case, the UK has never fielded a land-based nuclear force.