is it really 50/50?

Sa
People will say oh well you have a 50/50 chance of it being a girl or boy but is it really a 50/50 chance. Isnt it possible some men really only produce female sperm or male sperm. If he shoots 100,000 sperms and 90,000 were boys then you would have a 1/4 chance of having a girl. lol Idk just a shower thought because we find out gender next week. Do you think my thought is accurate?