I agree that the increase in vocab might be a factor. My DS has had similar issues lately in going to bed. Saying "Mummy come back" alot and crying. When you go back he is just wanting to chat about anything from Mummy wearing shoes, want to clean teeth again, want to get up etc etc
I have now been refusing to get drawn into the chat just cuddling briefly in the cot until calm then saying its sleeping time now Mummy loves you very much and will see you in the morning and then coming out. Tonight is the first time in a couple of weeks that I have not had to go back in at all
Some nights I have spent an hour coming in and out.
We also seem to have last molars on the move although nothing visible yet. Also can have up to an hour of chatting to himself - usually this involves things he has done in the day, although the crying is a more recent thing. We are not sure if this is delayed reaction to our DD.
I have been naming our wind down routing more as suggested in another post for the last few days so that might help. Ie saying now we will go upstairs and clean our teeth, chose our stories, read our stories then go to bed. Then saying now we have cleaned our teeth we will chose our stories, read our stories then go to bed etc repeating after each stage. This might be helping him know what is coming (although we have had the same routine forever so its not really a surprise
)
Good luck though - as you say it is nice to know other people are having the same issues.