In the NHK program "Meet and Speak", the phrases they use have a mixture of hiragana and romaji. Not as in hiragana on one line, and romaji underneath, but individual words being composed of the two, such as "すmimaせn".

![Example image](https://i.stack.imgur.com/z10ly.png)

What is the purpose of this mixture? Is is supposed to indicate pitch accent? Alternatively, is romaji used for hiragana that the program has not yet taught?