As you said that you were known to write /dev/sda* of your linux partition so I'm assuming it still didn't work which I suspected earlier why it might not work. That's why I asked you to upload the output of fdisk -l. In this output you will see an EFI partition. Check its corresponding name. Most of the time it is /dev/sda1. Write /dev/sda1 in the first command as mount /dev/sda1 /mnt.
Also upload the output here.
I'll soon create a thread on how to deal with this problem in UEFI-PC. I'm counting on you when you solve it. If that workaround doesn't work I've another edit but that should work.
Recommendations means if you doubt what other options may do then you can stick to recommended option. Though You can choose not to follow them. It doesn't mean that you won't be able to install kali if you don't follow them. Like professionals choose their own way. Instead of automatically partition the free space they may create manual linux partition and assign custom space for swap and home partition. It is upto you.
You still managed to install it without any problem. As you have successfully installed it, it doesn't matter now how did you install. This is what i was saying.