That makes sense from a DL perspective, because they are not on the hook for the downgrade compensation. They are merely giving you something back for the difference in fare.

You can take Tarom to the cleaners, but you'd have to ask yourself how much time that is worth for what is likely a reasonably inexpensive flight? 75% is likely not much. In contrast I had a downgrade on LH from F to J and they had to pay very very dearly for that, once I got legal representation.

Check what that one-way ticket costs when you buy it in J - 75% of that and then ask yourself whether it is worth the hassle ... you might get less than that, but it is max you could obtain.