That's not correct. On Monday they announce last week's purchases.
What's not correct, have you seen the Strategy website today?
I'll show you that today the Strategy company bought 535 BTC of Bitcoin at $80,340. Currently their average purchase price is $75,540. Which means their current Bitcoin holdings are 818,869 BTC.

Sources:
https://www.strategy.com/purchasesWhat is incorrect can be found both in the second sentence you quoted and in the image you posted.
You said:
It looks like MSTR will buy Bitcoin again tomorrow, given its twett at the X they used to do the day before buying. The last time MSTR bought Bitcoin on April 27, 2026 was 3273 BTC.
They don't buy on Monday. On Monday they announce last week's purchases. On the imagen you posted it says 'reported'. See this for example:
Strategy buys 535 bitcoin for $43 million days after signaling potential BTC salesStrategy purchased 535 bitcoin for about $43 million last week at an average price of $80,340 per coin.
Last week’s purchases were funded by $42.9 million raised through sales of the company’s common stock, according to a May 11 SEC filing.
They spread the purchases during the week and the following Monday they report the total purchases.
The same happened as for 4/27/2026, that you mentioned above, they didn't buy that day, they reported the previous week's purchases that day.
I think with this explanation it should be pretty clear now.