Does a post-doc in Mathematics help getting a Data Science job?
There was perhaps a time where a math Phd would be an immediate ticket to a data science position but I think that phase has come and gone. The reason? It has a simple answer: Tensorflow. 

Tensorflow is essentially all of Google's Phds getting together, writing out the formulas for a large number of data science models and, in the process, that takes a lot of the math out of data science. And this makes sense since most math in data science is "write one code" anyways. 

In a similar vein, DataRobot is effectively the best Kaggle competitors in the world getting together and also taking a lot of the math out of data science. 

So, I hate to be the bearer of bad news, but the math Phd just isn't attractive to most data science teams.