Why textMeshPro makes gc when called SetCharArray?

Question

I am new about unity，I found that in the function named SetCharArray, like this:

    public void SetCharArray(char[] sourceText, int start, int length)
    {
        PopulateTextBackingArray(sourceText, start, length);
        m_IsTextBackingStringDirty = true;
        m_text = InternalTextBackingArrayToString();
        m_inputSource = TextInputSources.SetTextArray;
        PopulateTextProcessingArray();
        m_havePropertiesChanged = true;
        SetVerticesDirty();
        SetLayoutDirty();
    }

there is a line with m_text = InternalTextBackingArrayToString();. The method InternalTextBackingArrayToString internally calls new string(array);, which can cause garbage collection issues due to memory allocation.

How can I avoid GC problems when using TextMeshPro Or am I misunderstanding something?

I tried a test like:

public class TestText : MonoBehaviour
{
    TextMeshProUGUI text;
    char[] chars = new char[12];

    static readonly char[] numbers = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9' };
    void Start()
    {
        text = GetComponent<TextMeshProUGUI>();
    }
    // Update is called once per frame
    void Update()
    {
        chars[0] = numbers[UnityEngine.Random.Range(0, numbers.Length)];
        chars[1] = numbers[UnityEngine.Random.Range(0, numbers.Length)];
        chars[2] = numbers[UnityEngine.Random.Range(0, numbers.Length)];
        chars[3] = numbers[UnityEngine.Random.Range(0, numbers.Length)];
        chars[4] = numbers[UnityEngine.Random.Range(0, numbers.Length)];
        chars[5] = numbers[UnityEngine.Random.Range(0, numbers.Length)];
        chars[6] = numbers[UnityEngine.Random.Range(0, numbers.Length)];
        chars[7] = numbers[UnityEngine.Random.Range(0, numbers.Length)];
        chars[8] = numbers[UnityEngine.Random.Range(0, numbers.Length)];
        chars[9] = numbers[UnityEngine.Random.Range(0, numbers.Length)];

        text.SetCharArray(chars);
    }
}

the result is: enter image description here