Greater Anglia are saying this about extension tickets.
Thank you for contacting Greater Anglia Customer Relations regarding your over 60 oyster card.
To confirm, the service you take does need to stop at Harold Wood for you to use the ticket from Harold Wood to Ipswich.
As most direct services have Stratford as the last valid station for the Oyster card, you will most likely need to get a ticket from Stratford to Ipswich.
The 60+ Oyster Card is an off-peak zones 1-6 travelcard with a few TfL related extensions. As a zonal and season ticket, the train DOES NOT need to stop where you change from one ticket to another. Please quote condition 14.3 of the National Rail Conditions of Travel to them.
If they’ve said this using public social media then please reply with the link and I’ll put them right publicly.