I've just been playing with this on the National Rail site (new version). It doesn't make any attempt to communicate the Network Railcard restrictions - if you pick a time when the railcard doesn't apply, it doesn't discount the ticket and (in the click through details, just says 'Railcard not applied'). Doesn't say why it's not applied.
If you select a time when the railcard is valid, this is the detail screen.
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The 'More information about this ticket' section (
https://www.nationalrail.co.uk/ticket-types/tickets/sor/ ) clearly says "Anytime fares are fully flexible walk-up tickets with no restrictions on when you can travel." and makes no mention at all of the need to check railcard validity.
On the final review screen (before being redirected to a vendor) it mentions the railcard, so would be the sensible place to put a warning about the railcard validity period.
If I click through to the vendor, again, no mention of railcard restrictions and a clear statement 'Flexible ticket with no time restrictions on when you can travel'
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The 'More info' option just says "Please make sure you bring your Railcard(s) with you." . If they can show that message, then there's no obvious reason it couldn't be expanded to say "
Please make sure you bring your Railcard(s) with you. Please check the Railcard restrictions to ensure your ticket is valid on the service you choose to use - some time restrictions may apply"