[sv-ac] Q: clock inference for $past in sequence

In a sequence, is a sampled value function required to infer a clock from the sequence declaration, rather than the sequence instantiation?     This is how tools I'm using interpret the current LRM language in 16.9.3, though this difference vs the ##n operator seems counter-intuitive for some users.

If this is correct, was it done intentionally, or is it an unintended side effect of our wording?

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// Code below generates compile error due to no clock for $past, even though clock is in context when sequence instantiated
sequence sig_is_stable(sig);
  (sig == $past(sig,1));
endsequence

property prop3(untyped sig, int upto);
   @(posedge clk) disable iff(reset) trigger |-> sig_is_stable(sig).matched;
endproperty

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