No. Heavy lifting actually increases the risk of back injury and pain and is certainly contra-indicated during recovery from injury.
Most definitely NO!!!! Avoid loaded spinal flexion when the lumbar spine is injured.
It's commonly been thought that back problems are caused by weak muscles, so therapy focused on strengthening exercises. But compelling research has shown that instead the problem is lack of stability and endurance in the muscles that support the spine. Many, many muscles have to work together in just the right way to support the spine, especially under load.
One of the best things your dad can do, as soon as he can, is to walk briskly. I would go 20-30 minute walks throughout the day and especially right after waking up. Rest and ice the area after each walk. Secondly, he could do stabilizing exercises such as the plank and side planks, trying to gradually increase the time but not the loading. If he is very weak or severely injured, he may have to start leaning against a wall rather than the floor, to reduce the loading.
I personally have little confidence in the physio. Standard exercise prescriptions can make many back problems worse. If you can find one who is knowledgeable about the spine-stabilization research, s/he may be helpful.
Hope your dad makes a speedy recovery.