How can you chain active fields in R6 classes that are field wrappers? - method-chaining

Question

I'm looking at the code example provided in the R6 class documentation here.
This is the class definition:
Person <- R6Class("Person",
private = list(
.age = NA,
.name = NULL
),
active = list(
age = function(value) {
if (missing(value)) {
private$.age
} else {
stop("`$age` is read only", call. = FALSE)
}
},
name = function(value) {
if (missing(value)) {
private$.name
} else {
stopifnot(is.character(value), length(value) == 1)
private$.name <- value
self
}
}
),
public = list(
initialize = function(name, age = NA) {
private$.name <- name
private$.age <- age
}
)
)
The important part is how the age field is wrapped to be read-only, and the name field is wrapped to perform a validation check before making the assignment.
In my own usecase, I'm not interested in the read-only part, but I am implementing the validation logic. So, focus on the active field for name.
I do not understand why they are following the pattern to return self after the call. How can you chain together assignments? Assuming age wasn't read only, how would it look to try to assign age and name in a chain? I've tried a number of ways, and it never seems to work:
p <- Person$new();
p$age <- 10$name <- "Jill" # obviously doesn't work because how can you reference the name field of 10?
(p$age <- 10)$name <- "Jill" # this looks more likely to work but the parens don't help
p$age(10)$name("Jill") # Does not work, you can't invoke active fields as if they were functions.
# other syntax options?
So, the heart of my question is: if you're using active fields in R6 classes to facilitate some type-checking prior to assignment, you can't really chain those operations together, so why does the official documentation show returning self in the field accessors?