I'm glad to report that as of this morning the error with the GET protocol has been resolved.
For everyone using a ThingsBoard installation as a controller to manage/organize their data, please be sure to enable the "use simple http factory" option in the REST API node.
Personal Weather Station Upload Protocol
There are two ways for data upload:
A/ GET Parameters
There is an error in the description: actually, only the "POST" method works for both ways.
Trying to update a single station measurements using a "GET" request - as implied by the paragraph - will lead to "Error 400 - Bad Request" message.