Yeah I know what you mean; you can get 2% tolerance film caps, most PIOs are 10% or 20%. I have some Russian NOS 0.047 uF PIOs, they measure like 0.055~0.058 uF. Not good for an RIAA filter.
I have some Sprague 0.047 PIOs they measure 0.046 ~ 0.049 but they're only 200 volt parts.