Yes, that is accurate. Processing facilities are the most restrictive environment an inmate will typically encounter in the Georgia system because they are transitional by design. The rules at Piedmont are tighter across the board compared to a regular housing assignment, and the limited phone schedule you described reflects that. Two 15-minute calls on alternating days, with Mondays being a phone blackout, is consistent with what processing centers impose while inmates are being classified and assessed before permanent placement.
On tablets: processing facilities are not the place where tablet access is available. Those programs exist at designated facilities, and access comes after an inmate has been assigned to a permanent unit. The restrictions at the processing level are temporary, and once your person is assigned and transferred to their permanent facility, the environment opens up and additional privileges become available.
The processing phase is the least comfortable part of the system, but it is also the shortest. Getting letters out to them now keeps the connection going even when phone access is limited.