Question about a clause within a clause

This is a discussion about clauses I got from a website.
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Look at this sentence:

He burns easily if he doesn’t use sun cream.

This is a main clause, which contains a subordinate clause:

if he doesn’t use sun cream

The meaning intended by the writer or speaker is conveyed by the whole main clause. One part of this main clause is the subordinate clause if he doesn’t use sun cream.

But the remainder "He burns easily" is not a clause on its own; it is part of the whole main clause: He burns easily if he doesn’t use sun cream.

Of course the words he burns easily could stand alone as a main clause in a different sentence, or context, if they conveyed the writer’s full meaning; but in some cases the main clause is grammatically incomplete if we remove the subordinate clause.

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Is 'he burns easily not an independent clause?' Or have I just misunderstood what this is saying as this seems like a complete sentence to me?

Is it saying that it is not a complete clause in this case because it only part of a main clause; however, it can be a complete sentence if 'he burns easily' is all one is saying...

Can you please tell me if what they mean by this.