M1 Max MacBook Pro Very Slow SD Card Write Speed

TL;DR:

New fast SD card has very slow write speeds on my new 16" M1 Max MBP's built in SD card reader but writes fast from a Windows laptop's built in SD reader. What's going on? Is my SD card or my MacBook Pro hardware/software defective? Or is this expected and why?

Longer version:

Got a new Sony Tough 64gb SD Card (SF-M64T) which is rated UHS II, V60, Read 277 MB/s, Write 150 MB/s. Started using it on vacation in my Sony A7r III camera. On the camera, scrolling through images I took was laggy so I assumed that maybe the camera was starting to show its age. When I put in a different SD card and scrolled though images it worked perfectly fine, so then I assumed that my new SD card was defective. Oddly enough when I put the new card back in my camera, image scrolling was working fine and snappy again. But I wanted to make sure I didn't need to return it so decided to run some speed tests...which led me down the following rabbit hole:

Tested on my new 16" M1 Max MBP (MacOS Ventura 13.1) using the built in SD card reader. I tried Amorphous Disk Mark which gave expected read speeds ~240 MB/s, as well as Black Magic Disk Speed Test. Both had  surprisingly very slow write speeds:

• Amorphous: 24 MB/s 
• Black Magic: 7 MB/s (!!!), though also slower read speed 83 MB/s so not sure what to make of this test in general (I know it's for a much different use case but just trying various methods I'm aware of here).

I reran the tests and even picked the lowest file size I could (64mb) on Amorphous to more closely approximate raw picture file sizes, but it didn't make much of a difference. 1gb was the smallest Black Magic would allow me to test.

SD card tested w/Amorphous Disk Mark on M1 Max

SD card tested w/Black Magic Disk Speed Test on M1 Max (1gb stress file)

I also tried to manually transfer a 1.15gb file within Finder and use a stopwatch to time read/write:

• Read: ~5.5s -> ~210 MB/s
• Write: ~130 seconds -> ~9 MB/s

The built in SD reader is clearly capable of fast data speeds since it reads fast. So then I became worried about the card reader on my MBP being defective. So I ran tests on the SD card using my old Dell XPS from 2018 running Windows 10 using its built in card reader and got similar normal read speeds but much faster/normal write speeds!

Same SD Card tested w/Crystal Disk Mark on Dell XPS

I read apple discussions forums and saw that many people had horribly slow read speeds from the built in SD card reader, but that was resolved for many people after MacOS 12.2 (I'm on 13.1). This seems like a separate write speed issue. I know most people don't write to SD cards from their computers, but considering that I paid several thousand dollars for this "Pro" machine, I just want to know why it doesn't get anywhere near the rated write speeds to an SD card. The card seems to be functioning fine since I'm getting expected transfer speeds on a Windows machine. I don't have a separate USB-C card reader to test but I have a suspicion that it would write faster (I do have a USB-A SD card reader and a generic A to C adapter, but that combo gave hilariously slow read/write speeds so I think the adapter is the bottleneck there).

So what's going on here? Is the SD card defective? Is my MacBook Pro? Does apple just need another driver fix or is it a hardware problem? Am I putting way too much energy into this?...probably...definitely...but now I'm curious and really want to understand.

Thanks in advance if you made it this far and if you can shed some light.