I do see people online talking about using Excel to do knitting patterns.

I don't know if his grandma just "accidentally opened it"---maybe she heard about it from someone else---but it does look like it's a thing.

I'd probably suggest using a pixel art app or something instead, but, well, Microsoft Office is pretty much everywhere.

Reddit, 5 months ago:

https://www.reddit.com/r/knitting/comments/1rz5udj/creating_patterns_on_excel/

Knitting website, 15 years ago:

https://anniebeeknits.wordpress.com/2011/06/06/charting-in-excel/

Charting knitting patterns in Excel

I do all my charting in Excel, personally. Mostly this is sheer laziness, since it’s the software I know best from my day job, and I can’t be bothered to purchase or learn another program! Anyway, I had some tips and tricks to share with Glenna, and I promised I’d make her a proper tutorial. I’m hardly an expert (at Excel OR at designing) but maybe this will prompt some others to share their tips and tricks too. Here goes!

Knitting website, 16 years back:

https://www.chemknits.com/2010/01/how-to-make-knitting-chart-in-excel_9394.html?m=1

How to Make a Knitting Chart in Excel (Part 1 - Setting up the Chart)

A comment on my peptide beer cozy pattern page inquired how I was able to make the chart look so good. You can go to an office supply store and purchase graph paper. You can download graph paper online. But how can you easily make a chart of your own design and share it on the web? In this article, I will give you a tutorial for using Microsoft Excel to generate your knitting charts. In Part 2, I will discuss how to draw your chart and in Part 3, how to save and share your chart.

It looks like people have developed a set of conventions using Excel functionality to colorize cells based on the characters in them, so they can rapidly input patterns using the keyboard.

There's no way grandma would figure out how to turn every cell into a square.

Honestly, weirder things have been accomplished with spreadsheets

it's a good story, and it makes good feelings happen in your body when you believe it in good faith, so it might as well be true even if it isn't

Maybe this is his Grandma https://www.youtube.com/watch?v=9J8k3d9C1pw

Kinda oddly specific tho, tbf. One can have faith.

Well, why would they buy the office pack, and resizing all the column like this is not really that intuitive But it's a feel good story, so I chose to believe!