As they have strengthened the Birmingham - Scotlands with Pendlinos over the summer [1], some other routes are substituted with Voyagers. These may well stick to Euston - Birminghams but you may want to check that the 09:07 definitely isn't a 5 car Voyager (with the added disadvantage of a soggy breakfast roll in First).
[1] With no success - the 10:20 Birmingham - Edinburgh is regularly full and standing (in Std) from Crewe. The fact that Virgin offer cheap Advance tickets on the longer 08:43 to the Noth West via Birmingham doesn't help much, as the 09:30 is always more expensive. The same applies to the 10:52 from Edinburgh to Euston, where many people get cheap Advance singles through to Euston despite the longer journey.