Ok, basic lessons - refer to the flashlight wiki here: https://flashlightwiki.com/Light_Output_Measurements
Candela (kcd) varies proportionally with lumens. I prefer using kcd to compare, rather than distance because I can directly relate it to lumens. For example, you make some tweaks to improve amps to the LED, resulting in a 25% boost in lumens. You should expect to see a 25% boost in candela -- straight proportional.
Distance is calculate by:
dist = SQRT (candela * 4)
This results in a smaller percent increase in distance (meters) than you see in candela. It's kind of like lumens - doubling the lumens does not double the perceived brightness your eyes see. So we use lumens to compare total light output, not some unit the eyes can perceive, that's why we should use candela and not distance.
Example: 150 kcd doubled is 300 kcd. 150 kcd is 775 meters, 300 kcd 1095 meters. So from 775 to 1095 is not that significant - is it worth it then to double the candela? The MF05 is not double the head width of the GT90 so I wouldn't expect it to double the candela, it's a bump, a fraction, and that's what you are seeing.
So you think a jump from 2.7 km to 3.15 km is not enough? Ok, than stay with 2.7 km knowing that light could never be made to exceed 3 km with the same LED. I think the proportional increase is about right for the proportional increase in reflector width.
Distance spec values to me are kind of meaningless. On that page I referenced in the flashlight wiki it states throw distance is based on 1/4 lux, which is a pretty useless level. MythBusters determined you need 4 lux to navigate a room if your eye aren't adjusted to the darkness. To me, I would like to see at least 2 lux on a distant object to be able to see it somewhat clearly.
Doing the math, if you get 1/4 lux for a 150 kcd light at 775 meters, to get 2 lux, it's 278 meters. - big difference. It's all about the math, what you find as acceptable, and of course trade-offs for carry vs. throw.