yes but convention of BODY being a list in not mentioned in the SRFI.
Well, you are looking at an implementation, not the specification.
SRFI 31 Specification
Syntax
The following production rules are to be added to those of [KCR1998] (we reuse names of non-terminals).
<derived expression> --> <rec expression>
<rec expression> --> (rec <variable> <expression>)
<rec expression> --> (rec (<variable>+) <body>)
The syntax uses <body> which is defined in R5RS as:
<body> --> <definition>* <sequence>