There are many people who attempt or who complete various Data Science courses, but to be honest beyond intern level applications it’s not enough.
What is always being sought is how the knowledge is being applied and by extension are you capable of independent thought. The number of interviews I’ve sat in where a candidate simply repeats what was on the last course they did, shows a lack of application and lack of understanding.
I feel many of the courses on offer don’t emphasise the need to apply what is taught on the courses to prove that you have learnt the material. Some of the courses are just click next to continue.
Your absolutely right that by practicing and making that public in a portfolio is the way to go.