Slow/strange test results for newly cloned SSD

[noisetta]

Linux-distro: Linux Mint 21 (Vanessa)
Desktop Environment : Mate 1.26.0
KDiskMark Version: 3.1.2
FIO Version: fio-3.32

Laptop is a: Acer Aspire 315-42
Motherboard: Sleepy_PK v1.03

I just cloned a newly bought Western Digital Black SN770 and was expecting to get close to advertised read/write speeds (or exceed) but I'm not even close.

I don't see any option in the BIOS menu to play around with anything really..

What am I overseeing here? The results on KDiskMark are below:

And here is a screenshot from a benchmark run using the pre-installed "Disk" app on Linux Mint: