Why transaction history W1(X1)W1(Y1)W1(Z1)C1W3(X3)R2(X1)W2(Y2)C2R3(Y1)C3 is serializable？

Question

[enter image description here][1]I'm reading the paper Making Snapshot Isolation Serializable，it provide an example 2.1 in Section 2.1： SI history H1

It'a an transaction history under SI，and explains it was The H1 transactions are serializable in order: T1T2T3；as far as i known：

• If it's serializable as T1T2T3, there should not be R3(Y1)，must be R3(Y2)
• If it's serializable as T1T3T2, there should not be R2(X1), must be R2(X3)

Where did I go wrong in my understanding?

I have search on google and asked on poe，it didn't worked for me.

I have test it on PostgreSQL12, with SERIALIZABLE，it return：

ERROR:  could not serialize access due to read/write dependencies among transactions
DETAIL:  Reason code: Canceled on conflict out to pivot 316211150, during read.
HINT:  The transaction might succeed if retried.