That's not quite true. You can use a very dim green (not brown) safelight, briefly, after half way through development. The film is less sensitive due to being partially developed, and green happens to the color your eyes are most sensitive to so it can be bright enough (barely) to be of some use without fogging the film. Many people develop sheet film by inspection this way. Plenty of books give instructions.
Originally Posted by Karl A
It takes some practice to make useful judgements of density with the very dim light and film that hasn't been cleared in the fixer, but some people find it useful.