You have to see from Pali text itself, in Pali text, it is indeed mentioned that arhat doesn't have a power similar to Buddha. http://www.buddhanet.net/budsas/ebud/ebdha335.htm
So, Pali sutta clearly indicate that arhat is missing something. If you don't miss something, your power cannot be less than Buddha.
But, some practitioner said that arhat is exactly equivalent to Buddha. Then when it is ask that if arhat is exactly same with Buddha why the power can be different?
The typical reply is it is not necessary that power can become the reason why arhat is different with Buddha, because arhat realize Boddhi.
This is exactly the place where for Mahayana, the realization of Boddhi is just the realization of empty of inherent existence, empty of self, but not absence of characteristic.
We do not need a rocket science here. If arhat power is less than Buddha. Something must be missing.
And you should note not all Theravada practitioner accept that arhat = Buddha. From bhikku Boddhi article you should be able to see that he doesn't share that view.
Another aspect is you quote from Mahamudra: moonlight. If you continue to read until the chapter that talk about 4 yoga in Mahamudra, the third yoga is one taste , the fourth is no meditation.
Tashi namgyal actually said (which I can't remember the page) that it is extremely extremely difficult to go to the fourth yoga - no meditation. He said something like even this xxxx said he can only achieve yoga of one taste.
It is really not an easy way to be absence from character.
Let's say you are male.
Dzongsar tinpot he said that if I ask you to think you are a woman from tomorrow onwards, although you know man and woman essentially no difference, it is very very difficult. It is easier to teach a baby who is male and tell him you are woman, then tell you, you are woman tomorrow.
You should see here, it is already has nothing to do with the emptiness of self, because you can see they are empty of self. Can you can feel how difficult it is to even think you are a woman tomorrow?
This is because you have a very deep imprint about character.
This is what we call eliminating the smell. Cleaning the dirt is far easier than cleaning the smell.
When you see something, like flower, may be you can see oh now I can see that it is just appearance. But if you go to the next step where even don't see that as just appearance, it is extremely difficult.
There is a reason why tashi namgyal said go to one taste is already very good, not to mention No meditation.
It is not dangerous not able to see the absence of characteristic, you just don't have perfect omniscience.
You also cannot see the practice of Theravada and compare it with Mahamudra and dzogchen. In this lineage we are, watch out, they are such issue. So, you are in better position to learn to be free from character.
But in Theravada, you don't have this kind of thing. May be you are very good, so in your practice you can get deeper and see this issue and you can eliminate the characteristic. In this way, I don't say that you can't become a buddha from Theravada teaching, but it will be very tough, because you may not aware of such thing. If you can, probably it is by accident, due to your exceptional sharpness.
For the rest, Buddha must knock your head, wake up, not complete yet.