I think Blizzard probably spiced these numbers…
There’s no way for us to accurately track the size of the ladder right now, instead we have to do backway analysis based on the rating Blizzard claims is required for R1 (and then we can look at the rank of the person at that rating at that specific time and multiply by 1000, do that for both Horde/Alliance and add up the numbers).
The numbers show that we’re somewhere around ~405K+ eligble characters for BfA. That is more than WoD S1 (which had 320K eligble players) and 10mil+ players subscribed in the first season.
Here’s some reference data:
S1-S13: No data.
MoP S14: 275K
MoP S15: 375K
WoD S1: 320K
WoD S2: 150K
WoD S3: 300K
Legion S1: ~211K+
Legion S2-S7: No data.
BfA S1: ~405K+
Given that we know that it’s an old game a subscriber spike which could cause 405K eligble participants (matching approx. ~12M players, if we extrapolate a bit from previous sub/arena-playerbase numbers) is not very likely, not to say almost completely unreasonable.
In essence Blizzard is probably lying.