How sardines are cooked?

I emailed wild planet out of curiosity to ask how the sardines are cooked and they said they steam them first and then seal it in the can with liquid and cook them in a giant pressure cooker, tin and all....

Doesn’t this sound a little wierd or is this how all sardines are cooked? To be honest I thought they were smoked and then placed into the tin so I was a little concerned to hear this. Pressure cookers go to very high temperatures and I feel like the tin could release certain metals/toxins into the fish at such a high temperature