Why use data typed tuple compared to struct tuples?

[minewarriorsSchool]

So I was reading through the code conventions of f# and came across the following paragraph:
https://learn.microsoft.com/en-us/dotnet/fsharp/style-guide/conventions#consider-struct-tuples-when-grouping-small-value-types-with-high-allocation-rates

Here they say that struct tuple can be up to 40% faster then data typed tuples.

Question: considering struct tuple can lead up to a 40% increase and do not allocate memory, what holds us back from defining commands as

type Msg =
| CommandX of struct(bool * int * string)

instead of

type Msg =
| CommandX of (bool * int * string)

The same goes for our model: https://learn.microsoft.com/en-us/dotnet/fsharp/style-guide/conventions#consider-struct-records-when-the-type-is-small-and-has-high-allocation-rates

[TysonMN]

Nothing...I think