There's also the fact that the Klingon Empire is a large place, and certainly more diverse than it might appear. The Klingons make an effort to centralize and homogenise their society (ruled from the First City, shared uniform, etc.), but it's clearly a reactionary move given the divisions and conflicts that are endemic there, unless the Chancellor directs aggression outward toward alien targets. Different noble houses, different colonial fiefdoms and different fleets have competing and contrasting aims; it's entirely possible that there are many different ideas of "Klingon tradition". Indeed, perhaps something like the acceptability of homosexuality depends on which parts of the empire are in ascendance at a given time. I don't recall if we ever learned where either Krell or Lurqal are from, but we might speculate that, say, Beta Thoridor has a very homosexuality-tolerant climate, and native son Krell's ascension to the position of Fleet Admiral, along with other prominent and visible natives, has made it acceptable to openly engage in homosexual partnerships or matings? With the honour and political influence gained by these people, their cultural and social norms are in vogue, and so any old Qo'noSian laws condemning such things as open homosexuality are ignored. Perhaps with the loss of esteem that these people face in the years after "Affliction"/"Divergence", e.g. Krell's new status as QuchHa', the culture shifts again and another "Klingon tradition" becomes the more powerful, and among other things re-stigmatizes homosexuality (or indeed, at least certain forms of it)? This is perhaps akin to what we know happens with language, wherein the Imperial dialect becomes the "proper" way to speak and Klingons can gain and lose favour based on how well they speak the Emperor's Klingon.
My interpretation of the Klingons is that laws are either ignored or ruthlessly enforced depending on these cultural and political shifts, and are basically guidelines in the long-term. Which laws, standards and traditions are being enforced today depends on which factions hold sway. And any powerful political figure can dredge up an old law and make it apply where previously it was all but ignored. The Klingon society always exists in tension between the Klingon tendency to fly apart or decentralise, and the desire to keep the Empire unified; cultural standards and prejudices are probably ironically fluid, because the Empire needs to adapt to the constant shifts in power and prestige.
Short version: Lurqal's "Klingon tradition" might be distinct from Krell's.
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