Is it true that Thursday night (malam Jumaat) is a recommended night for intimacy?

No authentic hadith specifically commands intimacy on the night before Friday; it is only an interpretation of some scholars.
This view comes from a hadith about the virtue of bathing on Friday, which some scholars interpreted as an allusion to marital relations. But it is an interpretation, not a clear command. Likewise, the claim that intimacy on certain nights causes children to be born with defects has no authentic basis. The principle is that lawful relations are permitted at any time except during menstruation, nifas, the daytime of an obligatory fast, ihram and iʿtikaf. See Etiquette between husband and wife.