They don't seem to have much choice. Adding more P cores would them require to either increase the already ridiculous power limit even further or reducing the core frequency and risk losing some benchmarks to AMD...
Everyone somehow seems to only have glanced at the power graphs of 12900K reviews.
From couple different reviews only 8 P-cores enabled at 125W limit benches quite favorably against 5800X. Computerbase.de also benched 12900K with only 8 P-cores enabled at 88W limit to match 5800X eco mode with only a couple % behind.
Intel has a choice. Or at least it is not power that limits the choices. As pointed out above - ringbus becomes inefficient at 10-12 stops. Also P-cores take up die size - not quite at 1:4 rate against E-cores but close to that.
Other than lack of HT/SMT E-cores have roughly Skylake/Zen+ performance level. Sometimes a bit better (mostly INT), sometimes worse (mostly FP).
This seems to be the general concensus, but: for home server builders? hell yeah, bring me all E-core clusters, don't care how slow they are (Xeon Phi style).
Intel had 16-core Atoms a few gens back (Goldmont,
C395x) and had or has 24-core Atoms last gen (Tremont,
5962B which looks like is only available to some cell tower specific uses).