Are populist parties (still) challengers?

I've just read the umpteenth article considering (almost all) populist parties as challenger parties.
This conclusion is disconfirmed by empirical reality and is grounded on this FALSE assumption: COALITIONABILITY = GOVT. RELEVANCE

1) As I argued , more than 40% of contemporary populist parties have experience in national government (and this number has grown since last year). But there is (much) more... https://doi.org/10.1017/gov.2019.21

2) By focusing on a very narrow outcome (govt. participation), for the purposes of identifying 'challengers' crucial interactions taking place at the systemic level are overlooked. Basically, we miss a key element to understand party system functioning.

3) Indeed, last year I've found that across all European countries, a clear majority (66.7%) of populist parties present the property of systemic integration, meaning that they possess coalition potential and are viewed as coalitionable at the national level.

4) Conversely, only one-third of contemporary populist parties lack the property of systemic integration, and are relegated, either because of their volition or that of the others, to the margins of the party system. These latter parties are *really* challengers.

5) Why it matters? It matters because coalition potential implies an impact on the functioning of party systems and often on governmental outcomes. Yet, studies using the 'challenger' paradigm overlook the impact on both policy outcomes and party system functioning.

6) Once a party develops coalition potential, it has crossed the threshold of legitimation. This means that the actual
participation in government becomes simply dependent on bargaining strength, programmatic compatibility or electoral results (cf. Sartori, 1976).

7) This means that the eventual participation of this party in a government is (no longer) a matter of general acceptance as political force, it is a matter of bargaining power, programmatic considerations and/or electoral results. Hence, it is no longer an issue of legitimacy.

8) Consider for example the case of the Danish People's Party (DF), which would be classified as a 'challenger' following the definition based on govt. participation. The DF has never taken part directly in government, instead preferring to participate in formal minority govts.

9) This was primarily due to the effectiveness of such a position: the party itself has underlined that as a support partner it has a much more influential and powerful status than the one it could have as a member of the cabinet, as many of its policy goals have been implemented

10) In addition to the policy impact of the DF integration, the party contributed to the consolidation of the two-bloc competition in the Danish party system.

11) To put is simply, if we focus on the very narrow outcome of govt. participation, which is also influenced by the broader features of a given political system, we miss key interactions at the party system level. The challenger "paradigm" is just too simplistic.