Both those explanations seem slightly off to me. My own suspicion is that it was because Chinese characters were associated with the language of administration (the class of scholar-bureaucrats in China), and women were not expected to serve in government positions. Since the educational purpose of learning characters was to produce government officials, and women didn't normally become government officials, then they automatically weren't expected to learn characters.
So "not given the same level of education" seems to have been written from a modern 'universal education' viewpoint. 'Masculine pursuit' makes it sound as if characters were a pursuit in themselves, which probably wasn't the case for most. Men learnt the characters for a purpose, not as a 'masculine pursuit'. While the exclusion of women from administration was no doubt sexist, it has different implications from saying that women weren't given the same level of education as men. The problem is that people interpret the past in 21st century terms, which isn't always a very accurate way of seeing things. As someone said, "The past is a foreign country".