This website contains age-restricted materials including nudity and explicit depictions of sexual activity.
By entering, you affirm that you are at least 18 years of age or the age of majority in the jurisdiction you are accessing the website from and you consent to viewing sexually explicit content.
Likely due to the phrase being added to over time.
https://en.m.wikipedia.org/wiki/Jack_of_all_trades
Another version is: “Jack of all trades, master of none, but better still than a master of one.”
A number of old phrases have been added to over time.