Correlated scalar subquery with STDDEV_POP() returns truncated/inconsistent results when subquery_cache=on

A correlated scalar subquery using STDDEV_POP() returns inconsistent values across rows for the same partition when subquery_cache=on.

For the same partition p = 1, the mathematically correct result is:
57.0087712549569

MariaDB behavior observed:

STDDEV_POP(v) OVER (PARTITION BY p) returns the correct value for every row
Plain scalar aggregate SELECT STDDEV_POP(v) FROM t WHERE p = 1 also returns the correct value
But the correlated scalar subquery
(SELECT STDDEV_POP(t2.v) FROM t t2 WHERE t2.p = t1.p)
returns:
correct value on the first row
then a truncated/rounded value 57.008800000000000 on later rows in the same result set

POC:

DROP DATABASE IF EXISTS st;

CREATE DATABASE st;

USE st;

CREATE TABLE t (

  id INT PRIMARY KEY,

  p INT,

  v INT

);

INSERT INTO t VALUES

  (1,1,12),(2,1,99),(3,1,-45),(4,1,7),(5,1,-88),(6,1,23),(7,1,55),

  (8,2,1),(9,2,2),(10,2,3);

-- Baseline: correct scalar aggregate

SELECT STDDEV_POP(v) AS sd

FROM t

WHERE p = 1;

-- Expected / actual correct:

-- 57.0087712549569 (display format may vary)

-- Baseline: correct window result

SELECT id,

       CAST(STDDEV_POP(v) OVER (PARTITION BY p) AS DECIMAL(30,15)) AS wf_sd

FROM t

WHERE p = 1

ORDER BY id;

-- Expected: same value on every row

-- 57.008771254956900

-- Problematic query: correlated scalar subquery

SELECT id,

       CAST((SELECT STDDEV_POP(t2.v)

             FROM t t2

             WHERE t2.p = t1.p) AS DECIMAL(30,15)) AS sc_sd

FROM t AS t1

WHERE p = 1

ORDER BY id;

Actual result on MariaDB 12.2.2:

id sc_sd
1 57.008771254956900
2 57.008800000000000
3 57.008800000000000
4 57.008800000000000
5 57.008800000000000
6 57.008800000000000
7 57.008800000000000