All the restrictions I am aware of are explicitly about work (Erwerbstätigkeit) and there are distinct visas to look for jobs that do not allow working so it would seem to imply that “looking for a job” is a distinct category and therefore OK to do as a visitor (being an EU citizen, I don't need a visa and I have no first-hand experience with that so this is only based on my reading of the rules).
As a Canadian citizen, you can indeed apply for a residence permit from within the country but it is merely a procedural difference (and it applies equally to other long-term visas, e.g. spousal visas). “Apply” means just that, it does not mean that you will get a permit “just like that” but only that, if you are already in Germany on a visa-free visit, you are not required to go back to Canada to request a change of status. But you still need a job offer to have any chance of success with your application. By contrast, people from most other countries are required to leave Germany, apply from outside and wait for a work visa somewhere else than Germany, otherwise the authorities won't entertain their application at all, even if they have an impressive resume and a solid job offer.
Do note that the recruitment process in Germany could be quite different from what you are used to in Canada. Traditionally you need to submit a whole file with certificates from each of your previous employers, all your grades all the way back to secondary school, a photograph of yourself, etc. Some startups use a more informal style and maybe having some highly sought-after skills or being a native speaker of English could help you land a job quickly but otherwise the process last several months from first contact to job offer. Since you do need to have an offer lined up to apply for the residence permit, that does not leave a whole lot of time to look for work on a 90-day visit (might it be what the embassy staff meant?).
Regarding IT jobs, “less regulated” means a lower salary threshold to qualify for some visas and a little less paperwork but you still need an authorization/residence permit in any case. See also Apply for a German working visa without Invitation for details.
