Limit tolerances specified to the ISO standard are by default applied by the principle of independency. The principle of independency only requires a simple two point measurement to verify size conformance along the entire length of the feature. To invoke the Envelope Requirement a symbol “Circle E” is clearly associated with the dimension and tolerance or a note.
Where you applied the straightness tolerance this is an additional requirement for the feature of size.
The ASME and tANSI standards invoke the Envelope Principle, Rule #1 (Envelope Requirement in ISO) by default for all feature of sizes.