Default properties for col-sm (-md, -lg, -xl) -* disappeared?

Created by: tomxc

In the v4 alpha 2 release (https://raw.githubusercontent.com/twbs/bootstrap/v4.0.0-alpha.2/dist/css/bootstrap.css), the following was present:

.col-xs-1, .col-xs-2, .col-xs-3, .col-xs-4, .col-xs-5, .col-xs-6, .col-xs-7, .col-xs-8, .col-xs-9, .col-xs-10, .col-xs-11, .col-xs-12, .col-sm-1, .col-sm-2, .col-sm-3, .col-sm-4, .col-sm-5, .col-sm-6, .col-sm-7, .col-sm-8, .col-sm-9, .col-sm-10, .col-sm-11, .col-sm-12, .col-md-1, .col-md-2, .col-md-3, .col-md-4, .col-md-5, .col-md-6, .col-md-7, .col-md-8, .col-md-9, .col-md-10, .col-md-11, .col-md-12, .col-lg-1, .col-lg-2, .col-lg-3, .col-lg-4, .col-lg-5, .col-lg-6, .col-lg-7, .col-lg-8, .col-lg-9, .col-lg-10, .col-lg-11, .col-lg-12, .col-xl-1, .col-xl-2, .col-xl-3, .col-xl-4, .col-xl-5, .col-xl-6, .col-xl-7, .col-xl-8, .col-xl-9, .col-xl-10, .col-xl-11, .col-xl-12 {
  position: relative;
  min-height: 1px;
  padding-right: .9375rem;
  padding-left: .9375rem;
}

but in the latest v4 dev version (https://raw.githubusercontent.com/twbs/bootstrap/e391fcb953cc959ddd88fb676b68f49eef85ef06/dist/css/bootstrap.css), there are no longer default properties defined for anything other than col-xs-*. The col-sm-*, col-md-*, col-lg-*, and col-xl-* classes are only defined inside media queries now. Was this an intentional change?

For example, if you have the following:

<div class="row">
  <div class="col-sm-8 offset-sm-2">
     Text
  </div>
</div>

then when the window width is less than 544px, there is no longer padding for the element.

Also, is it intentional that some units have changed from rem to px?

.row { margin-right: -.9375rem; margin-left: -.9375rem; }

to

.row { margin-left: -15px; margin-right: -15px; }