Why, if you set the height of the columns in bootstrap 4, then they do not stand on top of each other?

Question

Bootstrap

Started experimenting with bootstrap 4 and noticed some interesting column behavior.

<div class="container">
        <div class="row">
            <div class="block col-4">lorem10</div>
            <div class="block col-4">lorem10</div>
            <div class="block col-4">lorem10</div>
            <div class="block col-4">lorem10</div>
        </div>
    </div>

I set the row height to 100px and the columns to 10px.

As you can see in the picture, they do not stand one under the other, why?
What's stopping them? After all, this is not reasonable behavior.
Thanks in advance.

Answer 1

https://css-tricks.com/snippets/css/a-guide-to-flexbox/
align-content:
stretch (default): lines stretch to take up the remaining space