How would the P550 have "materialised"? It was only announced in June. It takes at least 12-18 months to go from a core being announced to someone incorporating it into an SoC and then manufacture that SoC, let alone have it in products in shops.
As is usual in the industry, any serious potential customer will have been able to get the full RTL for the core back in June or July, and evaluate its performance in simulators such as Verilator, or on FPGAs.
Claiming it's somehow not "real" is just stupid. There is no serious possibility that a core that boots Linux and runs SPEC etc in an FPGA won't work the same in a properly designed and manufactured SoC.
Benchmarks of the HiFive Unmatched are exactly what they should be given its A55-like microarchitecture -- a bit better than a Pi 3 and sometimes close to a Pi 4 on normal compiled C code. It doesn't have SIMD or specialised AES and SHA instructions, so of course benchmarks of that kind of thing are worse than a Pi. If that's important to you then of course don't buy one.
RISC-V International last month ratified a number of important extensions including Vector and crypto and those will start appearing in future chips.
There are several documented startups working on "M1 class" RISC-V cores, staffed with highly experience highly credible people such as Jim Keller or people who founded PA Semi and then developed ARM cores at Apple (including the M1).
There's no magic involved in making a top end RISC-V core, just money and good engineering.
