Select all will rename everything that you just imported into the Library. My workflow is to insert SD card, import by copying all files to designated folder within LR, then select all and rename. Couldn’t be easier. If it is a different folder than already established within LR, or a sub folder within LR, just add that folder/sub folder within LR. I keep original images on the SD card as a backup, as well as backing up in the other usual fashion known to most of us.
My workflow is to download the files from the card through Downloader Pro. It asks me for a "job code" which I make a short descriptive text string. All the files are renamed to include the job code, the date and the time. Downloader Pro places them in a folder named with the descriptive text. I have one text string to supply and it renames the files and names the folder. After downloading, I import the files to LR. Last time I tried it, renaming the files and placing them in a new folder took two entries in LR (one for the file names and one for the folder path). DP does it with one entry. (And I can select the files I want to run through DP, although I usually do the triage in LR).
I re-use all my cards. I don't think using the cards as backup is economical. I have 3 local disks and a cloud service.
I'm sure your method works for you, just as my method works for me. The main thing to consider is naming your files with some method at download/import time so you don't have to do it later. Once the files are in LR, I consider the name to be irrelevant since I use keywords for searches. I use meaningful file names just in case someone else who doesn't know anything about LR wants to look for a subject.