He is playing a dangerous game. I suspect he isn't really bothered by a "stiff" back anymore. So he can train normally now. But it is impossible that the back injury is completely healed. I therefore do not consider it impossible that, once he trains harder, or resumes the competition, he will have back problems again. Especially if he has to climb at a high level, on cobblestones.... And then what should happen ? The same story again, stop for a few weeks, then gradually start cycling again ? With a high probability that the result will be the same. Then we are already June or July.
There is a chance that the season is over when that scenario plays out.