I tried the simpler numeric encoding method of converting each 3-digit group into 10-bit words. I keeping the encoding rules above only for the last group. My Smartphone built-in scanner correctly read the code.

Encoding with variable length bit words do work (every scanner I have used, correctly read the QR-Codes I have generated with variable length bit words) but it makes decoding more complicated. However, this means that my source tutorial https://www.thonky.com/qr-code-tutorial/numeric-mode-encoding is not wrong.

Thanks for your fast replies. Special thanks for looking up what the ISO/IEC 18004:2015 QR code standard actually says. I didn't think of searching for the standard myself.