The default view is cut down for the user but I used two different content types and in the workflow email to the approver I used the full set of fields and form ID to select the correct form:
https://mysharepoint.com/workspaces/requestleave/Lists/Leave%20Request/EditForm.aspx?ID=[%Current Item:ID%]&Source=https%3A%2F%2Fharmony%2Eatradiusnet%2Ecom%2Fworkspaces%2Frequestleave%2FLists%2FLeave%2520Request%2FAllItems%2Easpx&ContentTypeId=0x0100438359F426C75C4F9C5FFC3017D2B451
The user gets a cut down field input view and a final full view after the approval process is completed https://mysharepoint.com/workspaces/requestleave/Lists/Leave%20Request/DispForm.aspx?ID=[%Current Item:ID%]
They can edit this afterwards but they can't change mid process.