Trainline monthly ticket with travelcard

I'm looking into buying a monthly season ticket with travelcard for a long commute, it says it includes a travelcard for London zones 1-6 but also says in the description something about the travelcard only being for 7 days? Is this an error or misunderstanding on my part because I don't get them selling a month train ticket and only 7 days worth of travelcard for tube etc??

You buy a monthly season ticket, and in addition for purchasing it, you get the travel card https://www.toptiplondon.com/transport/tickets/underground-tickets-travelcards (yes it lasts 7 days)

Season tickets in London
If your regular journey is between 2 National Rail stations within Zones 1 to 6, for example East Croydon and London Victoria, you can buy a Season ticket for travel exclusively on that route. For greater flexibility, for example if you also wish to travel elsewhere within London, you might want to buy a Travelcard.
For travel only within the London Travelcard area
If your journey is entirely within the London Travelcard area, a Travelcard Season ticket offers unlimited travel in the Zones and period for which it is valid, on National Rail and Transport for London rail services, London Underground, DLR, London Buses and, if valid in Zones 3, 4, 5 or 6, London Trams.
The Travelcard area and Travelcard Zones are shown on the London Rail and Tube services map. For Travelcard Season ticket prices use our Season Ticket Calculator. You can also view the full range of zonal fares on the Transport for London website.
Travelcards for 7 days or longer can only be added to your Oyster or train company smartcard – they are not available as paper tickets. Using Oyster or contactless pay as you go from Monday to Sunday will not cost any more than a 7-Day Travelcard for the same period, thanks to the weekly price cap. Find out more about price caps here.

https://www.nationalrail.co.uk/tickets-railcards-and-offers/ticket-types/season-tickets/