Wargaming stealth changed the way blueprint fragments are granted

I often like to take daily missions that grant blueprint fragments, because I am interested in many lines and don't want to spend any longer grinding than I need to.

Recently, however, I have noticed a change in the way blueprint fragments are granted to me. No longer does it seem completely random which vehicle I get a fragment on.

For example, before the most recent update, I had a grand total of one vehicle completely blueprinted by chance, the Ikv 103. Otherwise, the distribution of fragments was pretty random and even across the board, most tanks having at least one, some having up to 4, with one or two having 5. Every couple days it'd land on a vehicle I already had, and I'd get universal or national fragments.

However, since the most recent update, I've gotten not a single fragment for a vehicle above tier 5. I have gotten 3 vehicles completely blueprinted, them being the Matilda, Cruiser 3, and Sav M/43, which previously had 0 fragments.

Today, I got 3/4 fragments for the Cruiser 4, 1 for the sau 40.

Additionally, I have gotten zero national or universal fragments.

Normally this would lead me to believe that wargaming just switched the system to grant fragments from the lowest unresearched tier of a random nation, but this can't quite be the case, because I also got 2 fragments for the Type T-34 today, despite having never passed tier 3 in that tree.

Still, this is very, very suspicious. What are the odds that not a single vehicle above tier 5 would be assigned new fragments, nor a single already researched vehicle? The chances, especially for the amounts of fragments I get (usually 2-5 per day), would be incredibly small.

I feel such a change should have been noted in patch notes.

What do you all think?