jgsugden
Legend
Forest for the trees....Not meaning to put words in their mouth, but it looks like [MENTION=6780961]Yunru[/MENTION] was referring specifically to the issue raised in the OP (multiclassed caster having fewer spell slots than a single-classed caster with the same total levels due to the rounding rule). That's much more narrow than 'not behind in spellcasting'. And it's correct, as the Sorcerer/Warlock is not subject to the rule referenced in the OP.
If the problem here is that we round down and you end up slighty behind in spellcasting capability, then saying that the Sorloc does not suffer from this setback AT ALL (emphasis mine this time) is missing something.
This setback was intentional. They considered both it, and what the combinations with Warlock, would be like and were pleased with the result. The idea that the 'round-down deficiency' was an accident ignores that we had a lot of testing for this edition - likely more tha in any prior edition.