Has anyone else come across the useLegacyEncoding issue when upgrading to 7.10.4?

I followed all upgrade instructions, however, once I changed useLegacyEncoding to true, I still was not allowed to login.

I had to copy my old 7.5.13 web.config Membership Provider section into the new web.config in order for my login credentials to work as follows:

From the new 7.10.4 -

<membership defaultProvider="UmbracoMembershipProvider" userIsOnlineTimeWindow="15">
      <providers>
        <clear />
        <add name="UmbracoMembershipProvider" type="Umbraco.Web.Security.Providers.MembersMembershipProvider, Umbraco" minRequiredNonalphanumericCharacters="0" minRequiredPasswordLength="10" useLegacyEncoding="true" enablePasswordRetrieval="false" enablePasswordReset="false" requiresQuestionAndAnswer="false" defaultMemberTypeAlias="Member" passwordFormat="Hashed" allowManuallyChangingPassword="false" />
        <add name="UsersMembershipProvider" type="Umbraco.Web.Security.Providers.UsersMembershipProvider, Umbraco" />
      </providers>
    </membership>

To my old 7.5.13 Membership Provider section:

<membership defaultProvider="UmbracoMembershipProvider" userIsOnlineTimeWindow="15">
      <providers>
        <clear />
        <add name="UmbracoMembershipProvider" type="Umbraco.Web.Security.Providers.MembersMembershipProvider, Umbraco" minRequiredNonalphanumericCharacters="0" minRequiredPasswordLength="8" useLegacyEncoding="true" enablePasswordRetrieval="false" enablePasswordReset="true" requiresQuestionAndAnswer="false" defaultMemberTypeAlias="Member" passwordFormat="Hashed" />
        <add name="UsersMembershipProvider" type="Umbraco.Web.Security.Providers.UsersMembershipProvider, Umbraco" minRequiredNonalphanumericCharacters="0" minRequiredPasswordLength="8" useLegacyEncoding="true" enablePasswordRetrieval="false" enablePasswordReset="true" requiresQuestionAndAnswer="false" passwordFormat="Hashed" />
      </providers>
    </membership>

Why is that? Is there any way to use the new web.config code from 7.10.4, even if I change the useLegacyEncoding to true?