I agree. I think the market has shown that if not artificially hampered by the lack of schematics, parts, and DRM that even the most unrepairable seeming products can still be repaired.
A motherboard with soldered on components like RAM or CPU are still more likely to fail because of a bad capacitor or some liquid damage on the traces.
I think the GP meant that a motherboard with soldered-on components would be more likely to fail because of a bad capacitor or liquid damage than because of the soldered-on RAM or CPU, not more likely than other motherboards with swappable RAM and CPU.
You may have interpreted the statement the latter way. If interpreted as I suggested, surely it's fairly uncontroversial? Capacitors are quite notorious for failing.
A motherboard with soldered on components like RAM or CPU are still more likely to fail because of a bad capacitor or some liquid damage on the traces.