I have never planned weddings but I am familiar with EXCEL and want to confirm that no, such templates do not come with EXCEL. They must be third party software products.

All of it is just outrageously weird.

Also... again, I have never planned weddings, but I assume that in this day and age there are password-protected websites for planning weddings - just as with everything else. The websites usually offer a better user experience than EXCEL templates so it is weird that somebody would opt for an EXCEL template. Also, an EXCEL template is locally on his computer and findable by you. A website can be used via private browsing (every browser offers that - it is called different names, but it is available everywhere) without leaving traces on his computer. In other words, if he wanted to deceive you in such a MAJOR, MAJOR way (planning a wedding is a major thing; nobody has posted such a story on here), he could do that better with a website. That he would use EXCEL sounds completely ridiculous.