Non-floating columns in grid system

Based on an official Bootstrap’s example (v3.3.7), there is a trouble:

If we are in a media query and it is not applying a proper class on a column, by default the full width is reached (like a virtual col-*-12 class). However, the problem is that it is not floating as it should be.

Considering a portion of the said particular example:

<div class="row">
  <div class="col-md-8">.col-md-8</div>
  <div class="col-md-4">.col-md-4</div>
</div>

On a extra small (phones) or small (tablets) devices, children divs have no float: left.

[ghost]

Take a simple example, @ralfting:

<div class="row">
  <div class="col-lg-8">
    <h2>Title 1</h2>
  </div>
  <div class="col-lg-5">
    <h2>Title 2</h2>
  </div>
</div>

You can appreciate the differences between large and medium device (aside from the smallest): without float styles, there is margin collapsing in headings (and other possible unexpected behaviors).

[ghost]

You (@heikojansen and @ralfting) did not understand my explanation.

I know perfectly well there are 1 column per line for the smallest devices. The only problem (as I wrote previuosly) is that divs have not any float style declaration as expected.