I have been to several factories that have welding operations, in 4 countries. Yes they are normally behind a curtain or wall. This is, as stated, for safety reasons. It is the same reason that a welder wears a helmet with a dark visor. The arch of the welder can damage your eyes from a distance. The EDMs operate in the same manor, with a spark.
With that said they may want to hide some of their manufacturing processes that they consider IP or that might open the product up to tampering. As a manufacturing engineer, in a completely different industry, myself I learn little from the few minutes that the show spends on a factory floor. There are a few tidbits that stand out from time to time.