Thanks for your request. I recognize the usefulness of this feature, but it is difficult to implement it for now.

In BT, "pitch" is internally defined as 32 division of the seminote. Some effects, such as note sliding, require only simple pitch calculation since the "pitch" distance between adjacent seminotes is fixed.
In register-based pitch processing, the register pitch distance between adjacent seminotes is different for each pitch. Therefore, it is necessary to calculate the value that should be added to the register value at the time of execution of the effect, each time using a conversion formula to frequency.

Unfortunately, I did not consider switching between the two options in the early stages of development, so many parts of BT is implemented the pitch controller assuming the former. It is not easy to change the implementation because there are many parts to need the modification.
However, since the latter option is compatible with traditional MML, I would like to work on it in the future.