Really, you're just asking him to basically make your mod for you.
And to be frank, I don't blame him in the slightest for not wanting to put that much dedication into something that you'll end up taking the credit for anyway.
The manor and tone in which you request to Bombchu just reflects arrogance, as if you can guarantee that your mod will be good, even without providing any sort of details regarding your mod in the slightest.
Bombchu has his own work to deal with, and for him to use up his time to work on something that's not even his...well that's just ludicrous.
Despite this coming from someone who freely employs less than a dozen people, you can't just request someone's help for something where they clearly get the short end of the deal, and get angry when they reject your offer.
Also, a scam is defined as
"a confidence game or other fraudulent scheme, especially for making a quick profit; swindle."
For one, he's not profiting off this, at least from what I'm aware of, and he's evidently fulfilled requests which follow his criteria.
Your request however, is just too much for a simple request, considering how much ASM and time it requires.
It just can't be done in a day.
Bombchu has other things he needs to do (hopefully) and creating custom boss code takes an excruciating amount of time.