at the location https://docs.mongodb.com/master/faq/concurrency/index.html in documentation MVCC is not coming out accurately. There are several questions from Partners, Customers to prove or talk on concurrency on MongoDB/WT. Official documentation would help to share that message.
If the messaging is around - along with few diagrams it would help.
Multi-Version Concurrency Controls (MVCC)
– Keeps old versions of data while creating new ones
– No locks; read/write threads see data as it existed when the thread started
• Updates don’t happen in-place; a new copy is made
• Reads/writes see only data committed before they begin • If writes conflict, only one will “win”
• When writes happen: The new version of the document is first prepared
• The other write will will be retried based on the writes waiting on the update skip queue