This study does not conclude that a vegetarian diet is unhealthy for weaned children -- in fact, it concludes the opposite, that vegetarian diets are fine for weaning if parents are properly guided through the process.
If pediatricians are not properly equipped to guide through that process, then yes, it is a problem with educating pediatricians.
Health professionals need to be educated about what a healthy vegetarian diet looks like for children, because they are going to meet vegetarians who (very reasonably) are not going to accept an answer of "this is totally possible to do well, but I don't personally know how to do it, so nobody should do it." I think it's reasonable for the public to expect that those people learn how to address the health issues that the people under their care are facing.
If pediatricians are not properly equipped to guide through that process, then yes, it is a problem with educating pediatricians.
Health professionals need to be educated about what a healthy vegetarian diet looks like for children, because they are going to meet vegetarians who (very reasonably) are not going to accept an answer of "this is totally possible to do well, but I don't personally know how to do it, so nobody should do it." I think it's reasonable for the public to expect that those people learn how to address the health issues that the people under their care are facing.