What? If you mean other industries where people are called engineers is used then I'm pretty sure that getting up to speed in another industry and becoming familiar with the unspoken, unwritten, unconscious rules that make the product possible must take at least as long as in any kind of software based company. Not to mention that there are often lots of constraints regarding what may and may not be done with hardware exposed to the public.
If it takes folks more than a few months to onboard, you probably have too many rules, standards or other processes that are pointless. There a multiple exceptions but if you can’t onboard folks fast your management team is either incompetent or they don’t pay developers enough to care who learns.