How to use curly-curly operator and group by function

Question

I am learning R and trying to write functions that operate with column names as arguments. I am using rlang, and I need help understanding why am I getting some unexpected results when using the curly-curly operator and a group by function.

I don't understand why the second code chunk with the curly-curly doesn't work as I expect, any insight would be much appreciated. I am sorry if I made any mistake presenting the question or it is quite simple, I am learning.

Thank you so much.

This piece of code provides the desired result, with n counts for each different value found in the column "HLA_allele":

group_function <- function(.data, x_column){
  
  .data %>%
    group_by(.data[[x_column]]) %>%
    summarise(count = n())
}

Calling the function: group_function (selectedA, "HLA_allele") Output (expected):

# A tibble: 19 × 2

    HLA_allele count
    \<chr\>      \<int\>
    1 01            43
    2 02           113
    3 03            53
    4 11            31
    5 23            19
    6 24            53
    7 25            12
    8 26            18
    9 29            55
    10 30            27
    11 31            11
    12 32            20
    13 33            10
    14 34             3
    15 36             1
    16 66             1
    17 68            14
    18 69             3
    19 80             1

However, when I try to use the curly-curly operator I get one single result as shown:

group_function <- function(.data, x_column){
  
  .data %>%
    group_by({{x_column}}) %>%
    summarise(count = n())
}

Calling the function: group_function (selectedA, "HLA_allele") Output (unexpected):

# A tibble: 1 × 2

`"HLA_allele"` count
\<chr\>          \<int\>
1 HLA_allele       488

I've used ensym() as suggested here, and it works, but I don't really understand what's going on or why curly doesn't work here as expected.