I randomly grabbed the first 50 years of this century
Here are the dates of the Autumnal equinox, followed by the correct date for start of vesein tal umatar (some of these are Friday night when of course start is delayed for an unrelated reason)
Followed by the start date using your system followed by a Y if the y match and N if they don’t.
They are aligned 43/50 which is 86% pretty good but as a “rule” to keep sharing when it is wrong 14% of the tme I think you should stop sharing your system
Equinox – Correct date – your date – match?
2000 Sep 22 Dec 4 Dec 4 Y
2001 Sep 22 Dec 4 Dec 4 Y
2002 Sep 23 Dec 4 Dec 5 N
2003 Sep 23 Dec 5 Dec 5 Y
2004 Sep 22 Dec 4 Dec 4 Y
2005 Sep 22 Dec 4 Dec 4 Y
2006 Sep 23 Dec 4 Dec 5 N
2007 Sep 23 Dec 5 Dec 5 Y
2008 Sep 22 Dec 4 Dec 4 Y
2009 Sep 22 Dec 4 Dec 4 Y
2010 Sep 23 Dec 4 Dec 5 N
2011 Sep 23 Dec 5 Dec 5 Y
2012 Sep 22 Dec 4 Dec 4 Y
2013 Sep 22 Dec 4 Dec 4 Y
2014 Sep 23 Dec 4 Dec 5 N
2015 Sep 23 Dec 5 Dec 5 Y
2016 Sep 22 Dec 4 Dec 4 Y
2017 Sep 22 Dec 4 Dec 4 Y
2018 Sep 23 Dec 4 Dec 5 N
2019 Sep 23 Dec 5 Dec 5 Y
2020 Sep 22 Dec 4 Dec 4 Y
2021 Sep 22 Dec 4 Dec 4 Y
2022 Sep 23 Dec 4 Dec 5 N
2023 Sep 23 Dec 5 Dec 5 Y
2024 Sep 22 Dec 4 Dec 4 Y
2025 Sep 22 Dec 4 Dec 4 Y
2026 Sep 23 Dec 4 Dec 5 N
2027 Sep 23 Dec 5 Dec 5 Y
2028 Sep 22 Dec 4 Dec 4 Y
2029 Sep 22 Dec 4 Dec 4 Y
2030 Sep 22 Dec 4 Dec 4 Y
2031 Sep 23 Dec 5 Dec 5 Y
2032 Sep 22 Dec 4 Dec 4 Y
2033 Sep 22 Dec 4 Dec 4 Y
2034 Sep 22 Dec 4 Dec 4 Y
2035 Sep 23 Dec 5 Dec 5 Y
2036 Sep 22 Dec 4 Dec 4 Y
2037 Sep 22 Dec 4 Dec 4 Y
2038 Sep 22 Dec 4 Dec 4 Y
2039 Sep 23 Dec 5 Dec 5 Y
2040 Sep 22 Dec 4 Dec 4 Y
2041 Sep 22 Dec 4 Dec 4 Y
2042 Sep 22 Dec 4 Dec 4 Y
2043 Sep 23 Dec 5 Dec 5 Y
2044 Sep 22 Dec 4 Dec 4 Y
2045 Sep 22 Dec 4 Dec 4 Y
2046 Sep 22 Dec 4 Dec 4 Y
2047 Sep 23 Dec 5 Dec 5 Y
2048 Sep 22 Dec 4 Dec 4 Y
2049 Sep 22 Dec 4 Dec 4 Y
(I did this by hand so there might be a typo or error or 2, though doesnt change my overall point)