[jand]

As we are sharing anecdotes:

One of my school math teacher had the same approach in another way: We were expected to use greek letters, not latin ones.

Same reasoning: It showed us kiddos that the letter was insignificant compared to the concept expressed by the letter.

So my take would be: Your friend taught the students for the first time what they were actually doing while handling equations with "a letter in it". That is no problem of algebra in itself. It just means their previous teachers sucked.

[Viliam1234]

I saw a textbook that used a picture of a box in the equation. The number is hidden in the box, and you are supposed to figure out which number it is.