GT:RoF describes Near Bootes settlement occurring between c.-2150 (Sequoyah, Polyphemus) and c.-1800 (Vantage). However, the wheels must have come off quickly after the crisis of -1776, as by -1700 worlds in the Near Bootes Cluster were already experiencing TL declines and balkanisation.
The map of the Rule of Man in MT:Ref'sManual seems to suggest that the Rule of Man allowed the Terran Confederation some quasi-autonomy. However text sources refer to the Confederation being "dissolved" upon the establishment of the RoM. I suspect that if the Near Bootes worlds were colonised from Terra, which probably _was_ part of the RoM, then they were part of the RoM too (even if only nominally, even if only temporarily). On the other hand, MT:S&A refers to smaller states in Magyar and Alpha Crucis that "were neither part of the old Confederation nor the Rule of Man." So maybe you could throw the Near Bootes Cluster in here too.
The Terran Merc(h)antile Community (Combine) started to play some sort of governmental role from about -1700, but its involvement in the Near Bootes Cluster even at its peak was minimal. ("Close trade links between ... Mirabilis and Lagash.") Contraction of the TMC started almost immediately, and by the time of consolidation into the Old Earth Union, it only included the worlds between Terra and Forlorn.
Still from GT:RoF, the OEU (and other interstellar states in the Rim), really only started looking outwards again in the century between 100-200. Reference is made to OEU traders visiting worlds a couple of subsectors away for the first time in 250. And by 300, the OEU is starting to get involved in the Aslan border zone (MT:S&A), and the Near Bootes worlds are starting to send new colonies of their own out into Jardin subsector. However consolidation into the Bootes League to come a bit later than this. From this point onwards the Rim worlds appear to be increasingly prosperous Imperial Client States. However, T-prime worlds like Jardin (colonised directly from Terra, 16 parsecs away) remain uncolonised until as late as 450.
Let's put this together.
If there was any settlement rimward of the Near Bootes Cluster before 300, it was in a very minor way and may well have died out. After that time, there was the technological and economic potential to engage in large-scale rimward colonisation. However, the Rim states seem to have had a greater focus on political and economic empire building than astrographic expansion: the OEU is clearly a powerhouse politically, engaging heavy in the affairs of worlds one or two sectors away, but the persistence of the Dingir League, the Bootes League, and the Vegan Polity means that states are not expanding their borders in any significant way. We are probably looking at "empires" more like the French and Dutch ones rather than like the Russian and English ones. Settlements on vacant planets are likely done my small-scale private or social entities rather than as an expression of government policy.
Ergo, likely the worlds rimward of the Near Bootes Cluster remain clear of large-scale colonisation until the establishment of the Autonomous Region, if not later.
Similarly, imagine the situation of the Aslan. You've just developed J1 (TL9). You love expanding into vacant land, preferably without a fight. You see vacant worlds in one direction. In the other direction, you see a group of racially homogenous "clans" (human splinter states), each of which is rich and technologically sophisticated (multi-sector political reach, remember). These clans seem far more interested in making money off each other (and you), and don't seem to be overly interested in competing with you for the vacant worlds to spinward (after all, they have plenty of vacant worlds to rimward if they were interested in that). What would you do?
The Terrans were faced with pretty much the same situation, and pretty much tried the same sort of thing: expand _away_from the established power, trade, play for time, maybe we can co-exist after all. The situation was different in that: a) the Terrans were astrographically hemmed in, and b) the Ziru Sirka found the mere presence of independent Terrans (and their invidious ideas of innovation) an existential threat.