T&C say transferred points have to go into your FF account. T&C provided below:
- Marriott Rewards members requesting a Mileage Reward must be a member of the relevant airline frequent flyer program in order to receive a Mileage Reward.
- Once frequent flyer miles have been requested, miles will automatically be transferred to the member's frequent flyer account. Please allow up to six weeks for miles to be posted to your frequent flyer account. For some airlines, expedited services are available for an additional fee.
- Once miles are credited to the member's frequent flyer account, changes, reissuance or recredit of Marriott Rewards points are not allowed.
- The terms and conditions of the airline programs control the redemption and distribution of the miles earned through Marriott Rewards.
- The frequent flyer program names are registered trademarks of the airlines. The airlines reserve the right to change the frequent flyer program at any time with or without notice. The airline is not responsible for products or services promised or supplied by other participating companies.
Regarding devaluation, yes it will happen. Inflation is a fact of life with regard to all forms of currencies, whether it be FF miles, FS points, or cash.