Yes any led type of light, is a a throw away part.
I googled "mazda 6 gh rear light"
This company came up on the top:
https://www.buycarparts.co.uk/mazda/6-hatchback-gh/30892/10554/combination-rearlightI entered the details for a 2.2 165ps car.
It seems that there are three types of lights:
1. Bulb type
2. Led type
3. A combination of the two
I assume all of them should connect to the same plug but they look different. Some of them come with a 4/2010 date. So something happened around this date and the design changed or something.
If both your lights are the same and they work, then you have nothing to worry. If a led had gone, you need to buy the whole unit. In theory you can do open surgery to the old unit but if you do not know your way around, you may be better off with a new unit.
If you just want to change the lights for a different look, I suppose you could cross check with the shops and find out whether they fit. They have part numbers on the website.