I would think if as you say parables are not prophecy just as tongues are not we then will have our differences. Parables as the signified tongue of God like the time period when there were Kings in Israel. Parables were used to hide the gospel from those who refused to hear (sola scriptura)
God has set up a sign to help identify and perhaps commune with those who have that manner of spirit called falling backward to indicate judgment according to the letter of the law. The foundation of tongues as a law or doctrine of God. We must look to the law that reveals men falling backward. Another doctrine of God used in parables that give us the good news as a living hope. Because a person does not search out another level it does not mean they have no hope but a different kind or manner. It does not change the grace of God. Just another kind of understanding. Remember the faithless Jews turned the manner of inspiration upside down taking away the understanding of God. Parables as prophecy I believe can help keep the integrity of the gospel of grace..
Parables I believe the kind of food the disciples knew not of at first the meat of the word moved by the will of God to plant the gospel born again seed. its the clean food represented by a lamb as that which does not come out as draught but works in us to both will and do the good pleasure of God. It provides what is called the better things that accompany salvation. That God who does work in us promises he will remember all the good works we worked yoked with Emanuel
Clean hands ceremonially represent those redeemed. bread represents the word of God the daily will.
Matthew 15 King James Version (KJV)
Then came to Jesus scribes and Pharisees, which were of Jerusalem, saying,
2 Why do thy disciples transgress the tradition of the elders? for they wash not their hands when they eat bread.
3 But he answered and said unto them, Why do ye also transgress the commandment of God by your tradition?
4 For God commanded, saying, Honour thy father and mother: and, He that curseth father or mother, let him die the death.
5 But ye say, Whosoever shall say to his father or his mother, It is a gift, by whatsoever thou mightest be profited by me;
6 And honour not his father or his mother, he shall be free. Thus have ye made the commandment of God of none effect by your tradition.
7 Ye hypocrites, well did Esaias prophesy of you, saying,
8 This people draweth nigh unto me with their mouth, and honoureth me with their lips; but their heart is far from me.
9 But in vain they do worship me, teaching for doctrines the commandments of men.
10 And he called the multitude, and said unto them, Hear, and understand:
11 Not that which goeth into the mouth defileth a man; but that which cometh out of the mouth, this defileth a man.
12 Then came his disciples, and said unto him, Knowest thou that the Pharisees were offended, after they heard this saying?
13 But he answered and said, Every plant, which my heavenly Father hath not planted, shall be rooted up.
14 Let them alone: they be blind leaders of the blind. And if the blind lead the blind, both shall fall into the ditch.
15 Then answered Peter and said unto him, Declare unto us this parable.
Peter was not given the unseen understanding pertaining to ceremonial laws as shadows hoping the kingdom of God came by the temporal things seen walking by sight .
And again Jesus spoke another parable in a hope they would understand what it means to walk by faith the unseen eternal .
16 And Jesus said, Are ye also yet without understanding?
17 Do not ye yet understand, that whatsoever entereth in at the mouth goeth into the belly, and is cast out into the draught?
18 But those things which proceed out of the mouth come forth from the heart; and they defile the man.
19 For out of the heart proceed evil thoughts, murders, adulteries, fornications, thefts, false witness, blasphemies:
20 These are the things which defile a man: but to eat with unwashen hands defileth not a man.
Clean represent the donkeys that have been redeemed by the lamb of God .Not a source of redeeming. Just old farmers that live in the city. . . planting the incorruptible seed. . . that does not come out as draught.