Yes, they match. Here is the one from your form:
<input type="smsphone" name="SMSPHONE" placeholder="Your cell number (optional)"><br/>
And here is the one from an embedded form from MC:
<input type="text" name="SMSPHONE" class="REQ_CSS" id="mce-SMSPHONE" value="" style="border: none;">
I did pull the field from the buttons above the form. The type attribute is different but changing it to text doesn’t help.