I don’t understand why so much headache with a date field when you show the date on reviews as you wish anyway from the default WordPress.
Excel is a spreadsheet editor. It exports to CSV, but it is specifically made for spreadsheets which are intended to be visually viewed. CSV data is not. Dates can be inconsistent unless you specifically format the date column as one of the requirements CSV import formats.
Note that all formats require double digit months and days. US dates have the month before the day, EU dates have the day before the month. The reason why the CSV import is strict with dates is because when importing data into a website, the data has to be consistent, particularly when dealing with date formats.
For example: is 01/02/2024 January 2nd or February 1st? Depends on your location.