Maybe I'm a little slow but if the concept of 40% of the coins doesn't exist, how can you use it to compare it to an instamine?
What I meant was when you start talking about some percentage of some "initial period of faster mining" (and that is the only correct way to discuss percentages here) that sounds to me more like the system being set up from the start like an instamine, fast mine, etc. The faster period in this case is several years before emissions slow to some tail level.
It is a simple change to one or a few lines of code. I'm pretty sure that's not what you meant though, but that is literally the case. So "can be changed" is not really the issue, it is more like whether people want it changed. Ultimately it comes down to consensus of the community.