After working there for 6 years, I haven't seen a single up to date design doc. At best a high level diagram.
They are outdated as soon as implementation start, by different degrees depending on the project.
Side note but I think this average tenure number hasn't been updated in a very long time. In London for example, a third of employees have been here for more than 5 years.
US (where bulk of employees are) is still pretty close to 2 years unless that changed a lot in just a few years (I was a sr. dev manager there and worked there for around 6.5 yrs). This is pretty similar to the rest of big tech though except for Microsoft. England and Europe in general is a bad comparison since they have fewer options and very different working expectations.
They are outdated as soon as implementation start, by different degrees depending on the project.
Side note but I think this average tenure number hasn't been updated in a very long time. In London for example, a third of employees have been here for more than 5 years.