It is pretty normal, because for the most part you are still playing in your Elo against other players of the same level. Everyone may be soft set to a Silver level according to the system but in all reality you are still facing the same people you normally would, so it's basing that MMR off the MMR they had previously and just rebuilding.
I went 7-3 in season 3 placements and was still placed Bronze 5. So like I said, it's not anything new... it's also why I've since then found it better to NOT dive right into ranked within the first month or so of the season. The rank itself is just one thing though, the MMR might be higher than it so they can climb easily afterwards if they are able to keep a steady winrate.