Mask files for INT_L and INT_R

[Dario-CP]

Why do the mask files for tile types INT_L and INT_R (mask_int_l.db and mask_int_l.db) not exist in the database?
https://f4pga.github.io/prjxray-db/

In the documentation it is said that the mask file is needed for absolute frame address calculation.
How is this done for tile types INT_L and INT_R if no mask file associated to them exist?
https://app.readthedocs.org/projects/prjxray/downloads/pdf/latest/

Thanks