This is highly unlikely for an XKJ1 console. However, sometimes overlapping manufacturing dates create a "gray area" for consoles with other prefixes like XAW1 or XAJ7. If you see this, the site is correctly informing you that the only way to know 100% is to test with an RCM jig. But again, for a serial beginning with XKJ1, the hardware is definitively patched.
: This is not beginner-friendly . It requires "microsoldering" skills to attach tiny wires directly to the CPU and motherboard. is my switch patched xkj1 top
While the XKJ1 serial is a near-certain indicator, you can verify using the most reliable community tool: This is highly unlikely for an XKJ1 console