Unfortunately it’s not accurate. There are plenty of examples of smaller guys growing well and there are also examples of larger guys not growing. Starting size isn’t a good indicator of potential gains.
Things that definitely make a difference are:
Commitment
Heat
Doing the right routine at the right time for you
2” length gain and 1” girth gain are definitely achievable but they are also outliers. So, double down on the commitment. Throwing devices at the problem early on is probably a bad idea. Yes you’ll probably gain but if you do, you’d gain with manual methods and in the meantime learn how to PE and what your limitations for stress are. Bathmates are particularly useless devices because the have no pressure gauge and probably the most important part of pumping (beyond heat and cylinder size) is knowing what pressure you’re pumping to.
In terms of the time it might take, think in terms of years rather than months or weeks and be willing to make PE a part of your life for that time.