Bone marrow activity is directly related to hematocrit or hemoglobin level (hematocrit being roughly 3 times Hb level). To completely suppress bone marrow activity, the hematocrit has to be kept above 35%. This isn't practical because of the amount of iron that is introduced from taking so much blood, so the Hb is kept lower, with the pre-transfusion Hb in the 9-10 range. At this level, the attempted red cell production is still 2-3 times normal.
When intermedias do become transfusion dependent, they normally do not transfuse as frequently as majors. Since intermedias do produce some useful red cells, transfusion should be seen as a supplement and not a total replacement, as it is with major. One strategy is to induce fetal hemoglobin with hydroxyurea or other drugs, as is being done with Olivia, and taking an occasional transfusion when needed, because Hb has dropped temporarily, often due to illness. Occasional transfusions will do little to suppress bone marrow activity. My opinion is that transfusion should be avoided if possible. That depends on the long term success of the hydroxyurea and whatever new drugs come along, which is a matter of when and not if.