Hi Steve,
When I read the first part of your post this morning, something didn't ring true, but I didn't think that I knew enough to comment at the time. So I thought that I would polish up my knowledge of astronomy (I used to be very keen on it as an amateur many years ago), and do some reading on the physics of ocean tides. Perhaps I could present what I've found.
At the equinoxes, the axis of rotation of the Earth is perpendicular to the line joining the Earth and the Sun, so as the Earth rotates, all points on the Earth's surface have equal length day and night. The equinoxes don't in themselves have anything to do with the Earth, Moon, and Sun being in alignment. The unusual height of the spring tides this weekend, associated with the New Moon is most likely due to the fact that the syzygy coincides with perigee (the point in its elliptical orbit where the Moon is closest to the Earth). Because the moon is closer, the gravitational attraction on the ocean waters is greater, so the tides are higher. The coincidence of syzygy and perigee is often called a 'supermoon', and the associated tides referred to as perigean spring tides. If there was a correlation between unusually high tides and the perfect alignment of Sun, Moon, and Earth, we would expect to see those tides coinciding with eclipses (lunar or solar).
There seem to be a few sources that promote the idea that tides are higher at the equinoxes, but I was rather sceptical about this, and decided to read further. The physics is highly complicated, with several astronomical factors (sometimes described as harmonic constituents of the tidal wave-function) influencing the generation of tides in different ways. I haven't been able to come to a definite opinion, but at the moment I would suggest that any effect of the equinox is likely to be an order of magnitude less than the effect of the Moon being at perigee, and possibly pretty negligible.
If you (or any other reader) wants to investigate further, the Wikipedia article on Tides is a good introduction, but doesn't go into any effect of the equinox. I have also read the following internet sources, and there may be others I've not discovered.
https://faculty.washington.edu/luanne/pages/ocean420/notes/TidesIntro.pdf
https://tidesandcurrents.noaa.gov/publications/tidal_datums_and_their_applications.pdf (Pages 3-13 'Tidal overview')
https://academic.oup.com/gji/article/168/3/999/2044447
In the last one, an academic paper, it does say that peaks in solar semi-diurnal tides occur at equinox, but if anyone here can understand the sentence further down that explains why this is, they're smarter than me.
Angus
Angus; one of the Kent crew on TWO.
Tonbridge, 40m (131ft) asl