MoreType | new method to build data in RecyclerView with Kotlin | RecyclerView library

In the first case, you never "reassigned something new to inner". You created one slice of uint8, called inner, which you filled with values (overwriting those values several times), and you made every element of outer contain a copy of inner. But remember, a slice is only a view into an array that exists somewhere (in your case, the backing array is created anonymously by make). Copying a slice doesn't copy the values in the array, it just copies the slice header, meaning there are now multiple views onto the same storage (this is fine, and safe).

In the second case, you called make for every row of outer, so five different backing arrays were created, with inner pointing into a different one each time. This time, when you assigned inner to an element of outer, you got five genuinely different slice headers, instead of five copies of the same one.

In short: a slice is a value, but it's a value that contains a pointer. The pointer might point to an array that has a name, or it might point to an entirely anonymous array. There's nothing to worry about; Go will make sure that anything that is pointed-to stays alive.

This relates to this question: How to get generic Type? - but it isn't a real duplicate question, that's why I replicate it here.

While it doesn't answer the "Why", it gives the solution for the "How":

Helper function:

A slice is a view on an array. A slice will only create a new larger array and copy contents if the capacity is exceeded. A slice will continue using its original array if you truncate it. When you create a smaller slice, it is still using the old backing array with the contents leftover from the previous operations. When you append to that slice, it will continue using the same array until you exceed capacity.

The official Golang tour where you found that example [here] explicitly says:

To access the field X of a struct when we have the struct pointer p we could write (*p).X. However, that notation is cumbersome, so the language permits us instead to write just p.X, without the explicit dereference.