Earlier quoted context omitted.
Assuming Google has tens of thousands of software engineers (for a lower bound of 10,000) and artificial intelligence increases productivity by at least 0.01%, the first engineer has already been replaced.
So how long till AI will be fully replacing a SWE at Google? Notice parent said "fully"
It's like asking "How long until a bulldozer [1] fully replaces a human construction worker?" A bulldozer is not a full replacement for a human construction worker. However, 1 worker with a bulldozer can do the work of 10 workers with shovels. And 10 workers with bulldozers can build things no amount of workers with shovels can.
[1] I'm using bulldozer as shorthand for all automated construction equipment - front end loaders, backhoes, cranes, etc.