When I wrote “The first blob flag is a SKIP_EVM flag” I mean that there’s only one SKIP_EVM flag for the whole blob (namely the first flag of the first chunk, which happens to be the first blob flag). The other flags for other chunks are ignored by the parser and can be set arbitrarily, e.g. to squeeze extra data.
BTW, I’m now not sure the SKIP_EVM flag is a good idea because it complicates anti-replay logic to avoid non-EVM transactions being executed as EVM transactions and vice versa.