I'm not convinced that's actually seen as a benefit by any government either though, because it'd be bad for UK companies that sell here and also export - which is what you want really. Those companies can't lower their standards to compete with lower quality imports without losing their export business.
The outcomes have already penalised exporters relative to importers.
Exporting to the EU is hard: lots of standards checks.
Importing from the EU is easy: whole categories of imports are left unchecked, because new rules aren't being enforced as a matter of policy, which is the only way we have food security, for example.
Protectionism often seems politically appealing because its beneficiaries are highly visible and benefits are concentrated amongst a few larger firms. The beneficiaries of cheaper imports and freer trade are usually greater in total but thinly spread out - everyone benefits a little bit.
As such it wouldn't surprise me at all if both your perspective and GP's perspective are true - cheaper imports would be better for everyone but the government doesn't "want" them because they'd politically inconvenience a relatively small number of people very visibly.
