Maybe it is better to make the default value as in the standard ('simple') for $style

[jetsam729]

    protected function canonicalizeHeaders(array $headers, string $style = '**relaxed**'): string
...
    protected function canonicalizeBody(string $body, string $style = '**relaxed**', int $length = -1): string

https://tools.ietf.org/html/rfc6376#section-3.5
c= Message canonicalization (plain-text; OPTIONAL, default is "simple/simple").

Maybe it is better to make the default value as in the standard? -> $style = 'simple',