The three passages do not give three mutually exclusive "scripts" of the burning bush. They give three selective tellings of one encounter, each quoting true parts of the divine address for a different lesson.
Why the question has some force
The objection is not silly. In Surah Ta Ha, Surah al-Naml, and Surah al-Qasas, Moses comes to the fire and is called by Allah, but the wording is not identical. A critic says: if these are Allah's first words to Moses, why are they different? Was the first line "Indeed I am your Lord," or "Blessed is whoever is at the fire," or "Indeed I am Allah, Lord of the worlds"?
Put strongly, the critic argues that a real verbatim dialogue should be repeatable in one form. Variation, he says, looks like storytelling instability, and he may connect it to the verse about abrogation and forgetting as though the Quran itself offers an excuse.
What the verses actually claim
"And when he came to it, he was called, 'O Moses, indeed I am your Lord, so remove your sandals. Indeed, you are in the sacred valley of Tuwa. And I have chosen you, so listen to what is revealed. Indeed, I am Allah. There is no deity except Me, so worship Me and establish prayer for My remembrance.'"
Quran 20:11-14
"But when he came to it, he was called: 'Blessed is whoever is at the fire and whoever is around it. And exalted is Allah, Lord of the worlds. O Moses, indeed it is I - Allah, the Exalted in Might, the Wise.'"
Quran 27:8-9
"But when he came to it, he was called from the right side of the valley in a blessed spot, from the tree: 'O Moses, indeed I am Allah, Lord of the worlds.'"
Quran 28:30
Notice the key point: none of these passages says, "The only words spoken, in complete order, were..." Each passage says Moses was called, then it reports part of what he was told. The wording overlaps strongly: Moses is addressed by name, Allah identifies Himself, the place is blessed or sacred, and the majesty of Allah is declared.
Different selections are not contradictions
Classical scholars treated repeated Quranic stories this way: one surah may mention what another omits, because the Quran is not a stenographic transcript arranged to satisfy modern courtroom habits. It is revelation, guidance, and argument. Surah Ta Ha emphasizes Moses' election, worship, and prayer. Surah al-Naml emphasizes blessing, awe, and Allah's might and wisdom. Surah al-Qasas emphasizes the blessed location and Allah's lordship as Moses begins his mission.
There is no impossibility in Allah saying all of these things in one encounter. A fuller sequence could include: Moses is called; the place and those around it are blessed; Moses is addressed by name; Allah identifies Himself; Moses is told to remove his sandals and listen. The passages do not deny one another. They are partial reports of a longer address.
Also, when the Quran narrates ancient speech, it gives it in Arabic revelation. Moses did not receive Arabic sentences at Sinai. The Quranic wording is Allah's revealed wording to us, conveying truly what was said, while selecting and arranging the report according to the purpose of each surah.
Abrogation is not an escape hatch here
"Whatever verse We abrogate or cause to be forgotten, We bring one better than it or similar to it. Do you not know that Allah is over all things competent?"
Quran 2:106
This verse is about Allah's authority over revelation - especially rulings and signs - not a license for contradictions in historical narration. No Muslim needs to invoke abrogation to explain the burning bush passages. The ordinary tools are enough: context, partial quotation, and the absence of any claim that each account is exhaustive.
So what does the variation establish? It establishes that the Quran retells the same event with different emphases. What it does not establish is a contradiction, unless one first assumes that every passage must be a complete verbatim transcript of the entire exchange. The Quran itself does not make that assumption.