I added that:

oreAluminum+techreborn:ore#4
oreAluminum+immersiveengineering:ore#1

to the config file but it did not work. The blocks weren't registered as Aluminum Ore.

I tried to register Bauxite Ore as Aluminum Ore.

I tried here, and it is working fine, you sure that you added it to "userRegisteredOreDictEntries"?
because there is a similar config option, but to remove ore dict entriies. "userRemovedOreDictEntries".

on the next version these two options will be unified on the same option, the only way to differentiate them is the "+" and the "-" operators.

Here is the complete config file converted to .txt.
UniDict.txt

All other entries I added work.

Seems that something prevents the registration as oreAluminum.
BluSunrize/ImmersiveEngineering#2728

It seems to be an issue with Thermal Foundation. If it is not present registration works. https://github.com/CoFH/Feedback/issues/833

Yeah, it sure isn't an issue with Thermal Foundation.

I will keep on trying to find out what causing that issue.

I have no idea about what is causing this, I tried here with several names, and I could register them, but as oreAluminum, I couldn't, so... I have no clue....

Do you have Thermal Foundation present?

yeah, it is present here, probably you wants me to remove it and try again, right? XD

Yes. Try to register dirt as oreAluminim with and without thermal foundation. If you have the same issue tell me.

it seems to be working for Immersive Engineering Bauxite, but not for the Tech Reborn one.
really weird, more testing will have to wait till tomorrow, good night =P