They assume that the other ten questions got matching answers, and hence have given a compensation with a 100 point chest. They intended to reduce the questions to 10, but might have overlooked doubling the rewards for each question. Nonetheless, at the moment you can get potentially more rewards than usual due to the compensation.
The relevant update was described here. The relevant section:
► Optimized Soulmate questions: Now there are only 10 Soulmate questions.
The documentation from DA reads:
4. Optimized Soulmate questions: Now there are only 10 Soulmate questions but you will receive double rewards.
The doubled rewards have seemingly not appeared so far, that might be added in a later maintenance. Nonetheless, the compensation should make up for that somewhat, as the general rate of love dust to points tends to remain the same across medium and advanced chests.