Thank you for the question. En bloc breast implant removal refers to a procedure where the breast implant and the surrounding capsule is removed as a single unit. The procedures is performed such that the contents within the breast implant capsule do not come into contact with the surrounding tissues. Generally, the procedure requires a longer incision (6-7 centimeter) usually in the inframammary fold, in my experience. Also, in my experience, the procedure is more successful when capsules are thickened as opposed to when patients are very thin (normal) capsules. Also, sometimes complete capsulectomy is not safely possible; for example, breast implants place in the sub muscular position may have a capsule that can be densely adherent to the patient's rib cage. Removal of this posterior capsule can be potentially dangerous.
Generally speaking (in my opinion), unless the breast implant capsules have thickened (and/or are otherwise symptomatic), are associated with the ruptured silicone gel breast implants, or if the patient has concerns about "medical conditions" related to the breast implants, capsulectomy is not universally necessary. For these patients, en block removal of breast implants is a good procedure.
On the contrary (again), capsulectomy can expose patients to additional risks, such as bleeding, size loss, contour irregularities and other serious complications. In other words, any maneuver performed during surgery exposes patients to additional risk (morbidity). For example, attempting to remove very thin capsule densely adherent to the patient's rib cage may expose the patient to significant bleeding and/or entrance into the thoracic cavity.
You may find the attached link, dedicated to breast implant removal surgery concerns, helpful to you as you learn more. Best wishes.