Blogger feed request to get posts updated in last x days includes posts published but not updated in last x days

I created a test post and published it. Immediately after publishing (without any updates being made to it), I used BFTB app/program to view last 5 posts. The test post was listed at the top with an updated date-time which was 59 seconds after published date-time! But I had not updated the post at all - only published it. Here's the post output in the blog book (as text not HTML):

Test post

Published: Tue Apr 16 2024 12:08:00 GMT+0530 (India Standard Time)

Updated: Tue Apr 16 2024 12:08:59 GMT+0530 (India Standard Time)

Test post related to published date & updated date 

--- end post output ---

If this is the way Blogger handles all newly published posts which have not had an update, then if I choose to list default number of posts (25) updated in past 1 or 2 or 3 days, I should get all posts published or updated in the specified number of days (unless I have done lot of blog publishing/updates due to which number of matching posts is > 25 and in which case I can use up to 150 as max posts in the program form).