No, using AI to rephrase your own blog posts [unless it was unique] is not against Google's policies. However, it's important to note that AI-generated content must still be original, high-quality, and useful to readers in order to rank well in search results.
If you use AI to generate content that is low quality or doesn't provide any value, it won't help your SEO efforts. Here is Google's view on AI-generated content, an excerpt taken from Stacked Marketer Newsletter.
If you are planning to produce rephrased content in bulk, be sure to check some of the samples for plagiarism before further using or publishing the content.
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