December is the only month where a album can be released....
A decent 2 and a half month gap between albums...
They've released albums in the same month before in 2019 (City Lights and What a Life).
And even if you don't want to count that: Chen's 2nd album came out in October 2019 and Obsession came out in November of 2019 (and Super M also came out in October that year if that counts, but I don't think it does), Delight was late May 2020 and EXO-SC came out early July (just 6 weeks apart). And just last year Don't Fight the Feeling came out in June and D.O.'s Empathy came out in July.