When should I add curry paste? This week I was preparing Thai curry and something odd struck me when comparing the two packages of curry paste in my pantry. They're both from the same brand; the yellow curry says

Cut 300-350g of meat (substitute) or fish into pieces. Stir fry the curry paste for a short time over high heat and add the meat. Add 600g of vegetables and stir fry for another 2 minutes. Add 400ml of coconut milk (or less to taste). ...

but the red curry says

Cut 300-350g of meat (substitute) into pieces and stir fry until they're brown. Add 600g of cut vegetables and stir fry for another 5 minutes. Add the bag of curry paste and the 270ml of coconut milk. ...

Notice the difference when the curry paste is added. I've checked another recipe for red curry which says to add it first. I can imagine it makes a lot of difference whether it's in direct contact with a very hot wok, or just warmed up as part of the sauce. But what is the actual difference, and why would it differ between packages/recipes? Or would this depend on how it has been prepared before packaging? Also, suppose I have a package of curry paste which doesn't include a recipe, what's the general advice for it? Add it first or later?
(For those of you able to read Dutch, this is the yellow paste and this the red one. They're generally available at the supermarket known for its hamsters.)
You typically want to bloom the spices by cooking it over high heat for some period of time.  But if you cook it for too long, you risk burning the spices.
If you're trying to brown meat, the moisture in the spices both make it more difficult (because of the spices burning first), and throw off the color to let you easily tell when it's cooked properly.
When you're making a dish that cooks quickly (like fish) or that you want to stew more than brown, I'll cook the spice paste first, then add everything to it.
In general, my procedure for using spice pastes is:

Cook down onions or other veg that needs to soften and/or brown meat (optional)
Add spice paste
Cook for a minute or so (optional)
Add whatever remaining ingredients
Cook for another minute or so
Add liquid
Simmer until cooked through

I'm actually more surprised that your paste didn't mention cooking the paste for a minute or so, or letting it cook with the vegetables before you add the coconut milk ... but it's possible that it contained an ingredient that doesn't like high heat.
It's also possible that the goal for the red curry dish is for the individual ingredients to maintain their own distinct flavor with there being a sauce at the end, rather than it being more like a stew where the flavor meld together.