How do different browsers/devices handle font-weight?

Question

Codepen to reproduce

I've been working on this little drop-down list, when I noticed something odd. The font-weight property is display differently accross browsers and devices. In Firefox for example applying font-weight doesn't visibly change anything at all, while in Chrome the font-weight is rendered except for italic text [as expected Edge behaves exactly like Chrome] and on Android the font-weight works as it should.

---

The font-stack I use:

  font-family: -apple-system, BlinkMacSystemFont,
    "Segoe UI", "Roboto", "Oxygen",
    "Ubuntu", "Cantarell", "Fira Sans",
    "Droid Sans", "Helvetica Neue", sans-serif;

---

The font-weight is supposed to appear on hover:

.select .list .item:hover {
  font-weight: 500;
}

---

My code:

html {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Roboto", "Oxygen", "Ubuntu", "Cantarell", "Fira Sans", "Droid Sans", "Helvetica Neue", sans-serif;
}

body {
  display: grid;
  place-items: center;
  height: 100vh;
  margin: 0;
  background-color: #fafafa;
}

.select {
  font-family: inherit;
  font-size: inherit;
  line-height: inherit;
}

.select {
  position: relative;
  display: inline-block;
  padding-bottom: 7px;
}
.select:hover .list {
  display: inline-flex;
}
.select .list {
  position: absolute;
  top: 100%;
  left: 50%;
  transform: translateX(-50%);
  display: none;
  flex-direction: column;
  min-width: 180px;
  background-color: #fff;
  border: solid 1px #eceff1;
  border-radius: 4px;
  box-shadow: 0 0 8px -2px rgba(0, 0, 0, 0.125);
  box-sizing: content-box;
}
.select .list::before {
  content: "";
  position: absolute;
  left: 50%;
  height: 12px;
  width: 12px;
  background-color: #fff;
  border-width: 1px 0 0 1px;
  border-style: solid;
  border-color: #eceff1;
  border-top-left-radius: 2px;
  transform: translate(-50%, calc(-50% - 1px)) rotate(45deg);
}
.select .list .item {
  padding: 0.125rem 1rem;
  margin: 0.375rem 0;
  cursor: pointer;
}
.select .list .item:hover {
  font-weight: 500;
}
.select .list .group:not(:last-child) {
  display: inherit;
  flex-direction: inherit;
  border-bottom: solid 1px #eceff1;
}

<div class="select">
  <button>Button</button>
  <div class="list">
    <div class="group">
      <div class="item">Chrome</div>
      <div class="item">Safari</div>
      <div class="item">Firefox</div>
    </div>
    <div class="item" style="font-style: italic; font-size: .875rem;">Edit List</div>
  </div>
</div>