Full strength soils are fine for seedlings, allmix ocean forest or just some multipurpose compost all work well.
Rather than listen to people who say they are too hot listen to people who germinate in them.
Light mixes are for people that want to start fertilising straight away, all mixes are for those who want the soil to feed till next repot or not have to worry about feeding for a couple weeks or longer. An all mix can get you into mid flower without a fertilizer added a light mix won't assuming we're potting up from small to larger each time not in the final pot from start.
You would probably need to find a lot stronger soil than allmix to burn seedlings with, the ec is quite low for soil still.