Allah's apostle misunderstanding and bastardizing a Christian parable

Sahih Bukhari; Volume 8, Book 76, Number 565:
Narrated Abu Said Al-Khudri:
Allah's Apostle said, "When the people of Paradise have entered Paradise, and the people of the Fire have entered the Fire, Allah will say. 'Take out (of the Fire) whoever has got faith equal to a mustard seed in his heart.' They will come out, and by that time they would have burnt and became like coal, and then they will be thrown into the river of Al-Hayyat (life) and they will spring up just as a seed grows on the bank of a rainwater stream." The Prophet said, "Don't you see that the germinating seed comes out yellow and twisted?"

Bible (or the Injil, which Muslims are forbidden to read because it makes more logical sense than the Quran)

And he said, Whereunto shall we liken the kingdom of God? or with what comparison shall we compare it?It is like a grain of mustard seed, which, when it is sown in the earth, is less than all the seeds that be in the earth:But when it is sown, it groweth up, and becometh greater than all herbs, and shooteth out great branches; so that the fowls of the air may lodge under the shadow of it.
– Mark 4:30–2

The meaning of the mustard seed in the Christian context:

The parable compares the Kingdom of Heaven to a mustard seed which the parable says is the least among seed, yet grows to become a huge mustard plant that provides shelter for many birds.

In other words, something small and insignificant becomes something powerful.

The meaning of the mustard seed in the Muslim context:

Even having a little faith means you will eventually get out of the hell fire. However, you will become black and charred.

(Note that this logic is faulty because Muslims believe that you must first go to hell and pay for your sins before you go to heaven. You stay in hell in proportion to all the good things you did. Thus, if you were bad 1% of the time, you are in hell 1% of your after life. But, if the after life is infinite, that would mean you will spend the full after life in hell. --> 0.01/infinity = infinity) )

Further, Mohammad bastardizes the above parable by saying that having faith like a mustard seed makes one yellow and twisted, even if they go to heaven. As such, he is saying a person should have more faith than a mustard seed, and Mohammad makes an implicit assumption that having faith like a mustard seed is really pathetic.

1) Why did Bukhari include this hadith?
a) Was it to show that Mohammad, the illiterate prophet, did not really read the injil (bible) in coming up with his own parables?
b) Was it to show that Mohammad never read the injil (bible) to begin with, and as such, was not capable of making any ethical or philosophical judgments against Christianity, or any religion for that matter?
c) Or was it because by the time Bukhari wrote this, Muslims rulers commissioned him to write things that would demonize Christians, as the Christian doctrine is clearly far superior and logical coherent as compared to the Muslim docrtine, and any attack on Islam the religion could destabilize the political underinnings of keeping Muslim rulers as the ruling class?
2) Why did Mohammad not understand the biblical context of the mustard seed?
a) If Mohammad came to reassert the word of previous prophets and the messiah, why did he have to bastardize what they said?
b) Did Mohammad forbid the reading of the Injil (bible) to prevent muslims from finding out just how inept his own religious and theological background was?