It may depend on you. SD cards (and any other storage devices) should be umounted or ejected if you want to remove them. Otherwise the content can be corrupted.

The phone may be using different sized sectors, format it in Linux, & see if the phone can read it.

I used to format it in the phone or camera, linux usually can read anything. But anyway, good idea.

I would assume a fairly modern phone would format a card using exFAT. As stated if the phone is still powered on you would need to unmount or eject the drive. If the phone is buffering writes you might be pulling the card during a write operation. If you are using a really old card reader it might not support large capacity memory cards.

Yes it's buffering, too much buffering to make you think the card is fast. I admitted I did not always play nice with the card, but I will check the CPU and drive activities to see if the system is busy writing before pull the card, and sometimes it does not allow me to pull the card said its still in use, but I don't see the PC is doing anything, so that I will pull the card.
That lead to other problem, the photo app on phone delayed action due to the slow card, it took ages to show my photos, and when I delete or rename one it said done, but it was still in the queue, since I did not see it done so I do it again, and removed some photos that I want to keep, I think this is particular troublesome on Android !

I do not know what to say because in the last 10 years i have NEVER had a issue

I got few bad SD in couple years, also got some bad full size SD for cameras. The most reliable way to transfer phone's photos is still using the phone itself or via USB, although slow it will take care of everything. I've 70G of photos and data on the SD, and I copy them to SSD via USB that's not too slow I can get up to 30Mb/s, but when I write back to SD via USB I can only get 1/10 the speed, so I took my risk to copy via card reader. I can slowly get up to 10Mb/s in an hr. and 2.5hrs. to complete the transfer, this time I waited enough time to make sure the writing is completed before eject. I don't understand why SBC like the Pi designed to use SD as system drive, we could use adapter for emmc/m.2 etc. of course, but the SD is removable, the contacts may not be reliable as other media types just to say the least.

I have not tried any of such "endurance card", anyone ?

https://www.youtube.com/watch?v=dFt0Nafx_Pw

Heat was one of the causes of failure, especially when copying large files on a slow card