Is background-size property not animatable in IE11? - css

Question

I've been trying to get this text underline transition to work: https://codepen.io/shshaw/pen/pdyJBW
a, .strike {
color: #FF5151;
text-decoration: none;
display: inline;
background-image: linear-gradient(to bottom, transparent 20%, currentColor 21%);
background-position: 0 1em;
background-repeat: no-repeat;
background-size: 0% 6px;
transition: background-size 0.5s ease-in-out 0.2s;
}
a:hover,
a:focus {
background-size: 100% 6px;
transition-delay: 0s;
}
.strike {
color: #307672;
background-size: 0% 2px;
background-position: 0 0.5em; /*1em;*/
}
.strike:hover,
.strike:focus {
background-size: 100% 2px;
transition-delay: 0s;
}
html {
background: #000249;
color: #FFF;
font-size: 62.5%;
display: flex;
height: 100%;
}
body {
font-size: 1.6rem;
line-height: 1.4;
max-width: 30em;
width: 90%;
margin: auto;
background: inherit;
-webkit-font-smoothing: antialiased;
font-smoothing: always;
}
<p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Praesent bibendum, lorem vel tincidunt imperdiet, nibh elit laoreet felis, a bibendum nisl tortor non orci. Donec pretium fermentum felis, quis aliquet est rutrum ut. Integer quis massa ut lacus viverra pharetra in eu lacus. Aliquam tempus odio adipiscing diam pellentesque rhoncus. Curabitur a bibendum est. Mauris vehicula cursus risus id luctus. Curabitur accumsan venenatis nibh, non egestas ipsum vulputate ac. Vivamus consectetur dolor sit amet enim aliquet eu scelerisque ipsum hendrerit. Donec lobortis suscipit vestibulum. Nullam luctus pellentesque risus in ullamcorper. Nam neque nunc, mattis vitae ornare ut, feugiat a erat. Ut tempus iaculis augue vel pellentesque.</p>
<p>Vestibulum nunc massa, gravida quis porta nec, feugiat id metus. Strike me! Nunc ac arcu dolor, quis vestibulum leo. Cras viverra mollis ipsum, non rhoncus lectus aliquam et. Morbi faucibus purus sit amet lacus aliquet elementum. Donec sit amet posuere enim. Cras in eros id tortor fringilla ultricies. Mauris faucibus ullamcorper velit, pulvinar varius odio eleifend eu. Quisque id odio metus. Morbi adipiscing ultricies posuere. Pellentesque elementum porttitor eros in molestie. Maecenas ut leo quis nisi tempor tincidunt.</p>
<p>Donec nunc ligula, vulputate quis mollis eu, interdum quis libero. Donec nulla ante, facilisis sit amet vulputate at, tincidunt a velit. Maecenas vestibulum, nulla sed tincidunt viverra, lorem turpis aliquam urna, ut pretium orci purus consequat augue. Etiam a enim orci, vitae pulvinar odio. In elit urna, tincidunt a pellentesque et, scelerisque at nibh. Sed nec est sapien. Aliquam ullamcorper eros eu quam ultrices vel faucibus eros interdum. Etiam mattis eleifend sapien, eu iaculis massa feugiat sed. Aliquam erat volutpat. Vivamus facilisis ultricies eros, a pretium purus mollis id. Sed dapibus elit ut neque rutrum dignissim. Nulla eros nisl, venenatis quis rhoncus sit amet, molestie nec nisl. Pellentesque vel neque sapien, et sagittis nulla.</p>
<p>Aliquam eu iaculis mauris. Etiam arcu lectus, imperdiet sit amet volutpat vitae, commodo sed nibh. Fusce faucibus tempor cursus. Donec ut ligula tortor. Maecenas malesuada, diam vitae pharetra dictum, erat ante iaculis risus, sed sollicitudin nisl nisl vel metus. Nulla libero augue, convallis nec luctus id, iaculis nec urna. Cras vitae mi ut augue ultricies tempus.</p>
And I've got it working in all major browsers except IE11. I've seen this SO question (Background size animation not working in IE11 or Ipad) where the accepted answer says: "Internet Explorer 11's set of animatable CSS properties is the same like they've started in IE 10 with, and background-size is not among those animatable ones."
That answer also links here: https://www.w3schools.com/cssref/css_animatable.asp
Which lists the animatable properties, and lists background-size as one of those animatable properties, but when I try to run their example (https://www.w3schools.com/cssref/tryit.asp?filename=trycss_anim_background-size) in IE11, it doesn't work.
I can't seem to find any documentation that explicitly lists the animatable properties in IE11, so is background-size simply not animatable in IE11, and is there any documentation that says so?