Is it mandatory that partial ground breaks corresponding to a split activity that are longer than 6 hours or invade the Low Circadian Window (WOCL) take place in a suitable accommodation?

According to the normative point ORO.FTL.220: 

No. They can also be carried out in accommodation that does not meet the requirements of adequate accommodation. If it takes place in adequate accommodation, all partial ground rest (excluding post and pre-flight activities and travel) counts for the purpose of the extension of the maximum FDP, according to CS FTL.1.220(c) and (d). If it takes place in an accommodation (not suitable), the excess over 6 hours or the period that the WOCL invades does not count for the purpose of the extension of the maximum FDP, according to CS FTL.1.220(e).