nah the reason why thursday to thursday or w/e makes less sense than sunday to sunday and isn't just "the same seven days displaced" is because for some matchups, the foreigners especially, the monday-thursday after the weekend are just dead days, meaning they have significantly fewer days to prepare for their matchups.
for example, if reiku is playing pdc (hypothetical??), and reiku's spanish ass can only play pdc over the weekend, he only has two days or so to prepare for his game before the weekend where he has to play due to timezones. if that game gets missed (for any reason, such as pdc having an emergency fishing trip or his bar mitzvah or something), it's too early in the week to get an activity win forcing reiku to get subbed out b/c pdc is free whenever middle school gets out the remainder of the week.
if it's a sunday to sunday week, then reiku has the entire week to prepare for his game even if he can't play until weekend, and missing the scheduled weekend game is a lot more significant / less disadvantageous for less available parties
it might be the same number of days but those days are a lot less valuable after the weekend than before the weekend