Intel drivers don't report the amount of dedicated video memory to the operating system, the BIOS does. When applications ask "how much dedicated memory" that API call goes to OS, not to graphics driver. Sorry - there is no way for the graphics driver to trick the system here.
Consider - if application developers are stupid and read the wrong value out of Windows API calls, then how much would the BIOS have to steal to be safe? 512MB? 1GB? heck, for recent games like Assassin's Creed: Unity, maybe 2-3GB?
Its not a question of "chip melting consequences" as you so colorfully put it.
There are very good reasons why OEMs configure their BIOS with minimal (near zero) dedicated memory - Microsoft puts a lot of pressure on them to do so (and believe me, if an OEM couldn't get the WHQL logo from Microsoft for their system, they don't have a product). Why does Microsoft care? Because every megabyte of memory that is "stolen" at boot by the BIOS to be "dedicated" to graphics is not available for any other OS purpose. This means that Excel, web browsers, etc - pretty much everything will have less memory availabe and that means swapping to disk happens more often and degrades the overall experience. Maybe not an issue for you if you have 8GB of ram, but what about systems with 4GB? or tablets/netbooks with 2GB? If the BIOS stole 512MB at boot and it made everything sluggish just so that, on the occasion when you want to play games, the game will get an answer that makes it happy... that sounds like a colossal waste of memory and bad user experience.
Moreover, where do you stop? Here app developers are incorrectly interpreting data returned from an API call.. What happens if sloppy application developers pass the wrong parameters into functions? Should Intel try to "correct" that for them? what if they called the wrong function? If you are unhappy, your choices are to:
1) tell the app developer to get with program. As you know, Roblox isn't that demanding and would just fine on any recent Intel HD graphics if this issue was fixed. This is a huge potential market for them. If they made a one line change in their software they would fix this issue for millions of potential customers.
2) tell Microsoft that they need to provide an option where the DXGI api "lies" to the application and reports more dedicated memory just to make the apps happy without OEM BIOS/Intel having to actually waste memory simply to satisfy the app.