Confusing filtering by block hash behaviour in `listsinceblock` #25509

The reproduction speaks for itself:

diff --git a/test/functional/wallet_listsinceblock.py b/test/functional/wallet_listsinceblock.py
index fc06565983..e06fbf120a 100755
--- a/test/functional/wallet_listsinceblock.py
+++ b/test/functional/wallet_listsinceblock.py
@@ -32,13 +32,14 @@ class ListSinceBlockTest(BitcoinTestFramework):
         self.connect_nodes(1, 2)
         self.generate(self.nodes[2], COINBASE_MATURITY + 1)
 
-        self.test_no_blockhash()
-        self.test_invalid_blockhash()
-        self.test_reorg()
-        self.test_double_spend()
-        self.test_double_send()
-        self.double_spends_filtered()
-        self.test_targetconfirmations()
+        # self.test_no_blockhash()
+        # self.test_invalid_blockhash()
+        # self.test_reorg()
+        # self.test_double_spend()
+        # self.test_double_send()
+        # self.double_spends_filtered()
+        # self.test_targetconfirmations()
+        self.test_consistent_with_gettransaction()
 
     def test_no_blockhash(self):
         self.log.info("Test no blockhash")
@@ -383,5 +384,19 @@ class ListSinceBlockTest(BitcoinTestFramework):
         assert_equal(original_found, False)
         assert_equal(double_found, False)
 
+    def test_consistent_with_gettransaction(self):
+        """Test the filtering in listtransactions is consistent with gettransaction's
+        output.
+
+        The block hash parameter gives, according to the documentation, "the block hash
+        to list transactions since". Test that if we have a transaction confirmed at a
+        certain block, listing the coins since this block will output this transaction.
+        """
+        txid = self.nodes[2].sendtoaddress(self.nodes[2].getnewaddress(), 1)
+        self.generate(self.nodes[2], 1)
+        tx = self.nodes[2].gettransaction(txid)
+        coins = self.nodes[2].listsinceblock(tx["blockhash"])["transactions"]
+        assert txid in (c["txid"] for c in coins)
+
 if __name__ == '__main__':
     ListSinceBlockTest().main()

Is it intended that filtering transaction "since" block N only output transactions confirmed from block N+1?

(I don't really want the bug label, it might just be an issue with the documentation)

Note that this behaviour is tested, as including the passed block in the range for the depth check at https://github.com/bitcoin/bitcoin/blob/bae8a66d42d6c5b351879e15e1ab229a1324b18a/src/wallet/rpc/transactions.cpp#L650-L656 breaks other tests.

I think the idea is that you call listsinceblock with the hash of the last block you've seen before. And then you get all transactions that happened after that block.

If the behavior is changed to also include the block itself, to replicate the above, you'd need to pass in the hash of the successor block of the last one you've seen... which would require extra work.