The PRCA (Protestant Reformed Churches of America) has always defined "covenant" as friendship, which I have always said is a ridiculous step to make. Even if we were to agree that a covenant with God is only about friendship, that does not mean that the term "covenant" is to be defined as "friendship." The definition of words are not to be defined a priori according to theological presuppositions or dogmatic concerns, but rather through its usage historically throughout time (diachronic) and within its particular epoch (synchronic).
The term "covenant" in secular usage is normally associated with the Ancient Near-East or Greece, thus the terms berith (Heb.) and diatheke (Gr.) are defined as to their meanings in dialogue with the usage of "covenant" in the ANE and Greek contexts respectively. In the modern day, the word "covenant" is almost not used in the secular context, with the exception of politics, where its Latin equivalent (foedus) has given rise to the words "federation," "federal" as applied to a particular concept of governance, namely, that of an agreement between two or more parties for a political union (e.g. between the country and its states).
The words "federation," and "federal" refer to bilateral agreements. They need not be between equals, like states are not the same as the country. Yet, it is an agreement complete with stipulations and sanctions, and for the purpose of mutual benefit. Of course, for these modern usages, the concept is more along the lines of a contract, albeit a solemnly entered contract. Thus, it would fit more with the Greek term syntheke rather than diatheke because it truly depends on both parties honoring the contract. Regardless, we can see how even in its modern usage, the word has preserved some elements of what "covenant" has historically meant, which is a solemn agreement between two parties.
I guess since the PRCA with its denial of common grace focuses exclusively on dogmatics, I shouldn't be astonished about its rejection of linguistics for theological discourse. Yet, while certainly Scripture is primary, yet Scipture conveys its God-breathed revelation in human words, and God does not create two different meanings for the same human words: one as they are used in the immediate culture(s), and one for Scripture. God could always use the Hebrew and Greek words for "friendship" instead of berith and diatheke if he so chooses to convey that meaning of "covenant," yet He did not do so. The meaning of "covenant" as "an agreement between two parties" must therefore be the meaning God intends to convey when He uses berith and diatheke in the Hebrew Old Testament and Greek New Testament respectively, and we shouldn't think ourselves wiser than God as to what God intends to convey when He utilized those words.