My understanding (which is backed up by WDTC website) is that you cannot collect your tickets prior to your onsite check-in date if those tickets form part of a package.
That TPAS expert needs some remedial courses ...
You understand well, tickets cannot be picked up before the check-in day.
In a recent past, MYW tickets could be picked up in advance, but only up to 3 days before check in. Now Disney seems to have changed their policy.
But UK tickets bundled in a package are not valid until the check in day. And it's written in plain english on the WDTC-UK confirmation.
So, OP, you can do a split stay like :
1st week WDW with 14 days tickets and free dining for 7 days, any dining credit unused from that stay would be lost the day after your checkout day
2nd week offsite using your remaining 7 days but without dining
or a full onsite stay with free dining.
if you choose 1st week offsite, you'll need separate tickets, and a second week room only at WDW (no free dining then), or buy another set of tickets for the onsite stay, but that would negate a large part of the free dining savings.