In T 213/85 (OJ 1987, 482) the board stated that grounds sufficient for the admissibility of an appeal had to be analysed in detail vis-à-vis the main reasons given for the contested decision. If an opposition had been dismissed on the grounds of insufficient substantiation and the grounds for appeal merely disputed patentability without elaborating on the admissibility of the opposition, the appeal was inadmissible for lack of adequate substantiation (see also T 169/89, T 2001/14).
According to the board in T 95/10, there were three reasons for this: First, the appeal procedure is not a continuation of the opposition procedure, but a distinct procedure in which any facts, evidence or arguments considered relevant must, if need be, be resubmitted (see G 10/91, OJ 1993, 420; G 9/92 date: 1994-07-14 and G 4/93, both in OJ 1994, 875). Second, the appellant's analysis of the contested decision is needed in its statement of grounds of appeal. The third reason is that, in the absence of such an analysis, neither the board of appeal nor the respondent can establish why the appellant regards the contested decision as incorrect. It is, however, only based on this knowledge that the respondent can counter the appellant's arguments and that the board is in a position to reach an objective decision (see also T 1188/08, T 720/12).
In T 395/13, although the statement of grounds of appeal contained no substantive arguments addressing the reasoning of the decision under appeal, it nonetheless met the requirements of Art. 108 EPC in combination with R. 99(2) EPC. This was because the main objection of the appellant in the grounds of appeal was that the decision under appeal did not contain sufficient reasoning to enable the appellant to file such arguments. R. 99(2) EPC required no more than this and in particular did not specifically require that the statement of grounds of appeal addresses the arguments in the decision under appeal. The board therefore concluded that the appeal was admissible.