False, you’re linking to the X1 gen5, newest is gen12, which has a maximum of 32gb soldered, no slots: https://www.lenovo.com/nl/nl/p/laptops/thinkpad/thinkpadx1/t...
Also false, you can build a custom configuration of the gen12 with the 165U cpu and 64 GB of ram.
I just checked https://www.lenovo.com/us/en/p/laptops/thinkpad/thinkpadx1/t... and it says the laptop has two ddr5 slots, i guess you could load up to 128gb in there using the newest 64gb sticks.