Imagick creating PDF even though setImageFormat is set to JPEG

I have an odd issue that I cannot get to the bottom of. I'm using Imagick to generate JPG thumbnails of PDFs that are uploaded to a custom admin tool. However, Imagick is creating PDF files even though setImageFormat is set to JPEG and to add to the confusion this only happens when a PDF file has a single page. If it's a multipage PDF, the jpg thumbnails are created.

public function generateCopies() {
    if (empty($this->copyPathFormats)) {
        return True;
    }

    if (! is_array($this->copyPathFormats)) {
        throw new \InvalidArgumentException('Asset::copyPathFormat must be an array. '.gettype($this->copyPathFormats).' provided.');
    }

    foreach ($this->copyPathFormats as $key => $copyPathFormat) {
        if ($key === 'finder') {
            continue;
        }

        $path = $this->basePath.$this->pathParamSubstitution($copyPathFormat, $this->pathParam);
        if (! (is_dir($path) || mkdir($path, 0777, True))) {
            throw new \RuntimeException($path.' could not be found or created.');
        }

        $img = new \Imagick($this->path.$this->name);
        $img->setImageCompressionQuality( 89 );
        
        $copyName = $this->name;
        $format = $img->getImageFormat();

        if ($format === 'PDF') {
            $img = new \Imagick();
            $img->setResolution(150,150);
            $img->readImage($this->path.$this->name.'[0]');
            $img->setImageCompressionQuality( 70 );
            $img = $img->flattenImages(); 
            $img->setImageFormat('jpeg');
            $filename  = pathinfo($this->name, PATHINFO_FILENAME);
            $copyName = $filename.'.jpg';
        }

        $geometry = $img->getImageGeometry();
        $width  = $geometry['width'] >= $geometry['height'] ? $this->copySizeConstraints[$key] : 0;
        $height = $geometry['height'] > $geometry['width'] ? $this->copySizeConstraints[$key] : 0;

        if ($img->scaleImage($width,$height,False) !== True) {
            \RuntimeException('Cannot resize the image.');
        }

        if ($img->writeImage($path.$copyName) !== True) {
            throw new \RuntimeException('Cannot write the resized copy to '.$path.$this->name);
        }
        $img->destroy();
    }

    return True;
}

Solved the problem here. Even though the PDFs are indeed PDFs, they were exported from Adobe Illustrator. Imagemagick therefore was interpreting these as AI files. Once I updated my if statement to also include AI, things started working as expected.

$img = new \Imagick($this->path.$this->name);
        $copyName = $this->name;
        $format = $img->getImageFormat();
        

        if ($format === 'PDF' or $format === 'AI') {
                            
            $img = new \Imagick();
            
            
            $img->setResolution(150,150);
            $img->setColorspace(1);
            $img->readImage($this->path.$this->name.'[0]');
            
            
            $img->setImageFormat('jpeg');
            $img->setFormat('jpeg');
            $img->setImageCompressionQuality( 70 );
            $img = $img->flattenImages(); 
            
            $filename  = pathinfo($this->name, PATHINFO_FILENAME);
            $copyName = $filename.'.jpg';
        }