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.
P.S:
You are currently on the Digital Marketing Forum page; for more information on various topics that may be helpful, please visit Blog Posts (button below) and [share any content post you love] with your network.
[Boost your SEO blog post content creation efforts (easier than ever!) with this AI-powered tool]
[Want to grow & stay ahead of your competitors? - use these e-Newsletters to your advantage!]
[If you have any specific questions in mind, please drop a mail and I will answer through a post at the earliest possible time]. Check this forum frequently for fresh posts.