I once worked at a place that also said this, I hired on with a cadre of 5 other senior developers and two of them really took that to heart, and didn't do anything for six months. They were both PIP'ed (performance improvement plan) and out (left volentarily) at 8 months. A savy employee ought to take the "6 months to get acclimated" with a large dose of salt.

In the end, a truly "senior" developer doesn't need training on anything, just point them at the code, build and deployment scripts, and that's all they need.

I had a completely opposite experience one time. Was also told to take it easy for the first year, wasn't really given any real work to do, etc.

I did not want to waste time and lose my skills, so I talked to a few people here and there, found a few sharp corners in the product that many wanted to improve and started working on them.

Turned out, the reason behind the "relax for 1 year" rule was stack ranking. In order to promote the right people and award them bonuses, the management needed a steady flow of newcomers that would perform poorly and get abysmal review scores.