Reproduction steps:
1. Download and open the submitted project "directory_get_files.zip"
2. Build and run the project

Expected result: "/AAA" and "/AAA.file" are printed
Actual result: "/AAA", "/AAA.file", "/AAAB" and "/AAABC" are printed

Reproducible with: 2018.4.29f1, 2019.4.15f1, 2020.1.15f1, 2020.2.0b13, 2021.1.0a7

Reproduces on:
VLNQA00012, Samsung Galaxy S6 (SM-G920F), Android 7.0, CPU: Exynos 7 Octa 7420, GPU: Mali-T760
----------, Samsung Galaxy S9 (SM-G960F), Android 10, CPU: NOT FOUND, GPU: Mali-G72
VLNQA00321, Xiaomi MI 9 (MI 9), Android 9, CPU: Snapdragon 855 SM8150, GPU: Adreno (TM) 640
iPhone 6S (iOS 13.3.1)
MacOS Standalone

Does not reproduce on:
Windows Standalone

The following code causes the issue:
void Start()
{
Create("AAA");
Create("AAA.file");
Create("AAAB");
Create("AAABC");

string persitentPath = Application.persistentDataPath;
var files = Directory.GetFiles(persitentPath, "AAA.*");
}

Notes:
The issue does not reproduce when using Mono scripting backend.