Maybe he was near the end of his ink bottle and couldn't use as much as usual?
I'd rather be late with my delivery by one day, IF it were difficult to get another bottle in time, IF it would even need to come to that, rather than turn in substandard work. Such a situation would mean he was already very late (past the last deadline). If our inking would be substandard, it would be sent back to us to fix. If it happened again, our inking would be taken over by another inker. If he were a studio artist, and there were no additional ink bottles left, and they were so close to the printing deadline they couldn't wait for an office boy (runner) to run to the store to get more, and the supervisor told the artist just to ink lightly to have enough to finish, I guess that situation was possible. But, it sounds a bit far-fetched. But, I DO know that studios often had problems meeting the deadlines, and had to pay artists to stay up all night drawing, at times. So, I could imagine that happening. Much stranger things have occurred in the comic book industry.