I think the idea behind this offence was to give the possibility of a lesser offence being charged in cases in which breach of the safeguards was perhaps not as serious as it might be in other cases. It is true that the amendment would cause the penalty for this offence to match the penalty for murder. In that sense, it wouldn't be a lesser offence; it would be an offence of the same seriousness as murder.
One of the concerns that motivated the creation of this offence is that in jurisdictions that have these laws, breach of safeguards is sometimes detected, and yet there is very rarely any prosecution. That might be, it's surmised, because the choice is either to prosecute for the offence of murder or not to prosecute at all. The idea is to create a middle option, so that there can be a prosecution for an offence that more closely matches the wrongdoing.
The other point I would make, just from a pure criminal law perspective, is that medical assistance in dying might be provided by way of medically assisted suicide, and aiding a person to die by suicide is a less serious offence than murder. It carries a maximum punishment of 14 years and no minimum. There might be a strange impact on a physician who had aided someone to die by suicide whereby they could face a higher penalty for breach of the safeguards than they could have if they had been prosecuted for the offence of aiding a person to die by suicide.