Shakespeare employs feminine endings (a verse’s ending with an unstressed, hypermetric syllable) to provide rhythm and flow to his prose. These endings are gradually employed with more frequency in his writing. In his early work, they feature in under 10% of his written prose. Then they increase to around 20%. After 1600, they jump to over 25% of his writing, peaking at 35.4% of verses in the Tempest.
This was deliberately done to ensure that ensuing generations cracked the cypher and identified Shakespeare as the female writer she was. The increased frequency of the feminine ending was the author's way of trying to get the message across to the unsuspecting public without actually putting the fact in black and white.
This 'hidden code' is not a code at all but a writing style. The fact that Shakespeare frequently employs feminine endings to his verse is no more evidence of him being a woman than Herman Melville's frequent use of the word 'whale' in his prose is evidence that he is actually a whale.
[P1] Shakespeare's use of female endings was not typical for written works at the time. [P2] The author used it with increased frequency in later plays. [P3] This was a hint to readers that the author was, in fact, female.
[Rejecting P3] This is not evidence of anything.