font-feature-settings not working does not work if the letters are nearby

Question

so, text is in and has font-feature-settings: "ss03" on; but the property applies only to the first letter, or to stand-alone letters, why? [1]: https://i.stack.imgur.com/NGpl6.png

<span class="ss03">aaa a</span>

.ss03 {
  -moz-font-feature-settings: "ss03" on;
  -o-font-feature-settings: "ss03" on;
  -webkit-font-feature-settings: "ss03" on;
  font-feature-settings: "ss03" on;
  font-variant: small-caps;
  font-kerning: normal;
}

* { 
   box-sizing: border-box; 
   font-family: 'Circe', sans-serif;
}