The following code takes 10x more time on some Android 5.0.x devices.

var sw = new Stopwatch();
const int count = 30;
textures = new Texture2D[count];
sw.Start();
for (int i = 0; i < count; i ++)
{
textures[i] = Resources.Load<Texture2D>("sample");
}
var time = sw.ElapsedMilliseconds;
text.text = time + " ms" + ("(avg " + (time / count) + " ms)")

Steps:
1. Build and Run the attached project ("IO_SpeedTest_with_StopWatch.zip") on Android
2. Check how much time I/O operations took

Expected: 5ms / avg: 0ms (±10ms/±2ms).
Actual: 1000ms/avg: 25ms (±800ms/±20ms).

Reproduced with: 2019.3.0a3, 2019.4.17f1, 2020.2.1f1, 2021.1.0b1.
Not reproducible with: 2018.4.30f, 2019.3.0a2.
------------------------------------------
[Using StopWatch without unload]
Reproduced with:
VLNQA00108, LGE LG Leon 4G LTE, 5.0.1, Snapdragon 410 MSM8916, Adreno 306 (430ms/ avg 14ms)
VLNQA00042, Lge LG G3 (LG-D855), Android 5.0, CPU: Snapdragon 801 MSM8974AC, GPU: Adreno (TM) 330 - (1427 ms / avg: 47ms)
VLNQA00004, Meizu MX5, Android 5.0.1, CPU: MediaTek Helio X10 MT6795T, GPU: PowerVR Rogue G6200 - (250ms / avg: 8ms)

Not reproduced with:
VLNQA00012, Samsung Galaxy S6 (SM-G920F), Android 7.0, CPU: Exynos 7 Octa 7420, GPU: Mali-T760 - (1ms / avg: 0ms)
VLNQA00334, Xiaomi Mi A3 (Mi A3), Android 11, CPU: Snapdragon 665 SM6125, GPU: Adreno (TM) 610 - (12ms / avg: 0ms)
VLNQA00096, Samsung Galaxy S8 (SM-G950F), Android 8.0.0, CPU: Exynos 9 Octa 8895, GPU: Mali-G71 - (3ms / avg 0ms)
VLNQA00229, Oneplus OnePlus6T (ONEPLUS A6013), Android 9, CPU: Snapdragon 845 SDM845, GPU: Adreno (TM) 630 - (5ms / avg: 0ms)

--------------------------------------
[Using Time.time with unload]
Reproduced on devices:
VLNQA00042, Lge LG G3 (LG-D855), Android 5.0, CPU: Snapdragon 801 MSM8974AC, GPU: Adreno (TM) 330 (22.4s)
VLNQA00108, LGE LG Leon 4G ,LTE, 5.0.1, CPU: Snapdragon 410 MSM8916, GPU: Adreno 306 (5.9s)
N/A, Meizu MX5, Android 5.0.1, CPU: MediaTek Helio X10 MT6795T, GPU: PowerVR Rogue G6200 (4.5s)
(user's info) AQUOS EVER SH-04G (Tested), Android 5.0.2, Qualcomm Snapdragon 400, Adreno 330
(user's info) AQUOS PAD SH-05G, Android 5.0.2, Qualcomm Snapdragon 810, Adreno 430
(user's info) AQUOS Xx-Y 404SH, Android 5.0.2, Qualcomm Snapdragon 810, Adreno 430
(user's info) ASUS Nexus 7 2013 (Tested), Android 5.0.2, Qualcomm Snapdragon S4 Pro, Adreno 320
(user's info) ASUS ZenPad 8.0 P022, Android 5.0.2, Intel Atom x3-C3200, Mali-450MP4
(user's info) Fujitsu ARROWS NX F-02G, Android 5.0.2, Qualcomm Snapdragon 801, Adreno 330
(user's info) LG G Pad 8.0 L Edition, Android 5.0.2, Qualcomm Snapdragon 400, Adreno 305
(user's info) Samsung Galaxy Grand Prime SM-G530H, Android 5.0.2, Qualcomm Snapdragon 410, Adreno 306
(user's info) SONY Xperia Z2 Tablet SO-05F, Android 5.0.2, Qualcomm Snapdragon 801, Adreno 330
(user's info) SONY Xperia Z3 SOL26, Android 5.0.2, Qualcomm Snapdragon 801, Adreno 330

Not reproduced on devices:
VLNQA00334, Xiaomi Mi A3 (Mi A3), Android 10, CPU: Snapdragon 665 SM6125, GPU: Adreno (TM) 610 (0.51s)
VLNQA00096, Samsung Galaxy S8 (SM-G950F), Android 8.0.0, CPU: Exynos 9 Octa 8895, GPU: Mali-G71 (0.66s)
VLNQA00229, Oneplus OnePlus6T (ONEPLUS A6013), Android 9, CPU: Snapdragon 845 SDM845, GPU: Adreno (TM) 630 (0.53s)
VLNQA00176, Xiaomi Redmi 4 (Redmi 4), Android 6.0.1, CPU: Snapdragon 430 MSM8937, GPU: Adreno (TM) 505 (0.7s)
VLNQA00285, Samsung Galaxy J4 Core (SM-J410F), Android 8.1.0, CPU: Snapdragon 425 MSM8917, GPU: Adreno (TM) 308 (0.68s)
VLNQA00012, Samsung Galaxy S6 (SM-G920F), Android 7.0, CPU: Exynos 7 Octa 7420, GPU: Mali-T760 (0.56s)
----------, Htc Desire 510 (HTC Desire 510), Android 4.4.3, CPU: Snapdragon 410 MSM8916, GPU: Adreno (TM) 306 (0.63s)
VLNQA00313, Huawei Y6 Ⅱ Compact (HUAWEI LYO-L01), Android 5.1, CPU: MediaTek MT6735, GPU: Mali-T720 (0.71s)
----------, Samsung Galaxy S8 (SM-G950F), Android 9, CPU: Exynos 9 Octa 8895, GPU: Mali-G71 (0.51s, avg 0.017s)
----------, Xiaomi Mi 5s (MI 5s), Android 6.0.1, CPU: Snapdragon 820 MSM8996, GPU: Adreno (TM) 530 (0.57s)
----------, Htc M9 (HTC One M9), Android 7.0, CPU: Snapdragon 810 MSM8994, GPU: Adreno (TM) 430 (0.64s)
----------, Motorola Moto X (2nd Gen) (XT1092), Android 5.1, CPU: Snapdragon 801 MSM8974AC, GPU: Adreno (TM) 330 (0.68s)