Strange: Optyczne believes A9 III sensor might be ‘welded’ from two smaller sensors

There is an interesting discovery made by one of our readers:

I wanted to show you potential proof, that the Sony A9 III sensor might be ‘welded’ from two smaller sensors. As a part our test of this camera we always do 3-minute long ‘dark’ exposures to see how a device would behave in an astrophotography applications.
Here’s a 3-minute exposure with the lens cap on taken with an A9 III at ISO 51200: pliki.optyczne.pl/SA93/darki/SA93_i051200.JPG

You can clearly see a line in the middle of the sensor that may (but we obviously can’t be sure) suggest, that the A9 III sensor is actually two smaller sensors ‘welded’ together. For context – Arri does that with their larger format cameras. The Alexa LF has a sensor that’s two ‘standard Alexa sensors’ joined together. And for Alexa 65 they weld together 3 standard sensors.  And they’re pretty open about this, so such technology is proven to exist.

Here’s the chapter of the test containing the dark frame analysis: optyczne.pl/499.7-Test_aparatu-Sony_A9_III_Szumy_i_jako%C5%9B%C4%87_obrazu_w_RAW.html

Now, I do not have the engineering skills to investigate this. It seems very unlikely to me that two sensors were welded together. But perhaps some Sony engineers reading this post can give us an answer to this phenomenon?