The 75% rolling over is just for the transition phase, i.e. until 31 December
What happens after this has mostly yet to be negotiated
The UK has been unable to sign agreements, but has been gfrantically trying to negotiate to hav them ready to sign after Brexit
A few deals are for after transition, but the UK has not managed to retain all eu advantages
e.g. Switzerland:
What have the UK and Switzerland agreed on their trade relationship post-Brexit?
(references Swiss government information sheet, prepared mainly for Swiss companies)
https://tradebetablog.wordpress.com/2019/02/12/uk-and-swiss-trade-post-brexit/
Essentially, they are partly “rolling over” to the UK the present Swiss-EU trade relationship.
The roll-over is only “full”
- and ^only for goods, since services are not included at all -
^
during the transition in the UK-EU Withdrawal Agreement
when the EU asks the other free-trade-agreement countries to treat the UK as if it were an EU member.
Otherwise, a number of significant parts of the Swiss-EU agreements are “disapplied”.
The House of Lords EU committee has examined the Swiss "rollover":
https://www.parliament.uk/business/lords/media-centre/house-of-lords-media-notices/2019/march-2019/lords-eu-committee-report-on-uk-switzerland-trade-agreement/
"The Committee notes that
the Trade Agreement differs significantly from the precursor agreement which the UK is party to as an EU Member State.
These differences include:
Most trade in services,which make up 52% of all UK-Swiss trade, is not covered by the deal.
The Committee calls on the Government to explain its plans for future UK-Swiss trade in services.
The deal could place new limits on the export of agricultural products from the UK to Switzerland,
for instance raising the possibility that the UK will not be able to export products marketed as organic to Switzerland after Brexit.
Under the deal Switzerland will no longer recognise the Authorised Economic Operator status of businesses accredited as AEOs in the UK,
which would mean they lose access to benefits such as fewer controls at the Swiss border."