This is an issue created based on this one JBEAP-25163.

It looks that server responds with chunked transfer even in case the client use HTTP/1.0 in the request. Although, since chunked transfer was introduced in the HTTP/1.1, it's against the standard, see RFC2068#section-19.7.1:

However, a persistent connection with an HTTP/1.0 client cannot make
use of the chunked transfer-coding, and therefore MUST use a
Content-Length for marking the ending boundary of each message.

Changes in HTTP/1.1 vs HTTP/1.0 in RFC7230#appendix-A.1.3:

A.1.3. Introduction of Transfer-Encoding

HTTP/1.1 introduces the Transfer-Encoding header field
(Section 3.3.1). Transfer codings need to be decoded prior to
forwarding an HTTP message over a MIME-compliant protocol.

Also discussed here.

Truth is that not many applications use HTTP/1.0 now, so this issue isn't probably a big problem these days. Still it's a violation of the standard.