I compared the wwI and decaration and petition handwriting of the signature and they are the same.
I believe they are the same person unless you can find evidence to the contrary.
maybe an error but try using Jennie instead as wife.census takers get info wherever they can or make it up. For now don't worry abt shavel vs kovel. can sound similar to the uninformed.
btw did you read all the fascinating history of shavel lithuania under a googlesearch?(Siauliai or shavli.)
chag pesach sameach