Historically Intel did use non-standard EDA tools which is one reason they had trouble getting outside customers onto 10 nm (besides the fact that 10 nm didn't work). Some Intel acquisitions like Fulcrum and Barefoot never used Intel fabs.
I think they're supporting a more standard toolchain starting with 18A.
"For Intel, getting an external PDK out for a leading-edge process node is no small feat, as the company has spent decades operating its fabs for the benefit of its internal product design teams. A useful PDK for external customers – and really, a useful fab environment altogether – not only needs process nodes that stick to their specifications rather than making bespoke adjustments, but it means that Intel needs to document and define all of this in a useful, industry standard fashion. One of the major failings of Intel’s previous efforts to get into the contract foundry business, besides being half-hearted efforts overall, is that they didn’t author PDKs that external companies could easily use. "
I think they're supporting a more standard toolchain starting with 18A.